Low Profile Electrode Assembly

ABSTRACT

A tissue electrode assembly includes a membrane configured to form an expandable, conformable body that is deployable in a patient. The assembly further includes a flexible circuit positioned on a surface of the membrane and comprising at least one base substrate layer, at least one insulating layer and at least one planar conducting layer. An electrically-conductive electrode covers at least a portion of the flexible circuit and a portion of the surface of the membrane not covered by the flexible circuit, wherein the electrically-conductive electrode is foldable upon itself with the membrane to a delivery conformation having a diameter suitable for minimally-invasive delivery of the assembly to the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. application Ser. No.13/106,658, filed May 12, 2011, which is a continuation-in-part of U.S.application Ser. No. 12/616,758, filed Nov. 11, 2009, now U.S. Pat. No.8,295,902; which application claims priority to U.S. ProvisionalApplication Nos. 61/113,228, filed Nov. 11, 2008, and 61/160,204, filedMar. 13, 2009, and 61/179,654, filed May 19, 2009; and 61/232,756, filedAug. 10, 2009; and 61/253,683, filed Oct. 21, 2009; all of which areincorporated herein by reference.

Said U.S. application Ser. No. 13/106,658 also claims the benefit ofU.S. Provisional Application No. 61/334,154, filed May 12, 2010, theentire content of which is incorporated by reference as if fully setforth herein.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

BACKGROUND

Energy transmission to tissues can be used to treat a variety of medicalconditions. Electrodes can be used to deliver energy to tissues andcells for the purpose of sensing, mapping, ablating, and/or stimulatemuscles and/or nerves. Stimulation of muscles and/or nerves can be usedto trigger signals to the brain or directly to a specified musclecell/group. When the treatment requires removing or destroying a targettissue, thermal ablation therapy can be used to heat a target tissuewith a surgical instrument such as a needle or probe electrode coupledto an energy source that heats the probe tip, the target tissue, orboth. In such cases the thermal energy may be delivered directly byheating or cooling the probe or indirectly by generating energy fieldswithin the tissue which in turn generate heat, or both. Energy fieldscommonly used to create heat indirectly are RF and acoustic energyfields. The goal for most ablation procedures is to achieve cell deathquickly, precisely and with minimal to no collateral damage.

In the case of thermal ablation therapy for terminating destructivecardiac conductive pathways, energy can be delivered to the aberrantcells using minimally-invasive techniques such as an electrode-tipcatheter. Pulmonary vein isolation via radio frequency catheter ablationhas been demonstrated to be an effective treatment for some patientsexperiencing atrial fibrillation (AF). The cornerstone of the AFablation procedures is electrical isolation of relatively largepulmonary vein antra. Ablation of large confluent areas or lines ofablation with older generation AF ablation devices is accomplished bypoint to point manipulation and RF application with the single electrodetip. The single electrode catheter technique is extremelytime-consuming, complex and fraught by subjectivity. Furthermore,efficient and complete mapping of the electrical activity in targettissues often requires the placement of multiple catheters in the leftatrium, the use of a 3D-mapping, and/or steering system. It is oftendesirable to create relatively large surface area lesions withrelatively shallow depths of ablation.

Newer larger electrode arrays for “one shot” ablation have been used toimprove catheter ablation treatments. These ablation systems have beenadopted as a way to provide full contact to tissues having a complex 3-Danatomy and an overall larger lesion area. But known devices incorporateelectrodes that are bulky, stiff and limited in their ability to bepacked efficiently and effectively into the small space of the treatmentcatheter. The stiffness of these devices limits conformability againstthe tissue resulting in the need for additional repositioning andoverlapping patterns to ensure uninterrupted lines of ablation.

SUMMARY

One aspect of the disclosure is a catheter and electrode assemblycomprising: an elongate catheter body comprising a distal portion; anexpandable electrode structure coupled to the distal portion, whereinthe expandable electrode structure comprises an expandable membrane withan expanded configuration, and a branched flexible circuit having asubstrate layer and planar conducting layer electrically coupled to aplurality of radio frequency ablation electrodes and at least onesensing electrode, wherein in the expanded configuration at least fourof the electrodes are disposed in an array on a distal surface of themembrane.

In some embodiments the at least four electrodes are adapted to besubstantially coplanar with a distal tip of the catheter body when themembrane is in the expanded configuration.

In some embodiments the at least four electrodes are distal to thedistal tip of the catheter when the membrane is in the expandedconfiguration.

The assembly can additional comprise a first membrane portion comprisingat least 15% of the surface area of the membrane that is distal to adistal tip of the catheter body, and wherein the at least fourelectrodes are disposed on the first membrane portion. In someembodiments at least 10% of the volume of the membrane is distal to adistal tip of the catheter when the membrane is in the expandedconfiguration.

In some embodiments first and second opposite sides of a surface of themembrane are coupled to the catheter body.

In some embodiments a plurality of perforation holes traverse themembrane.

In some embodiments the assembly further comprises an annular introducerwherein the introducer surrounds the expandable membrane and confinesthe diameter thereof to less than about 0.2 inches. The introducer canbe adapted to engage a collapsed exterior of the expandable membrane andconfine a portion of the membrane substantially distal to the distal endof the catheter body.

In some embodiments the expanded configuration is an inflatedconfiguration.

One aspect of the disclosure is a unitary flexible circuit comprising: aproximal end, a distal end, and an intermediate portion, wherein theproximal end is coupled to an electrical source, the intermediateportion is comprised of a plurality of flexible branches separated fromone another along their lengths, wherein at least one branch has aninsulating layer along a portion thereof and at least one branch iselectrically connected to an electrode adapted to deliver radiofrequency energy, wherein the flexible branches conform to a portion ofa medical device adapted to be minimally-invasively delivered to alocation within a subject, and wherein the plurality of branches arecoupled to one another distal to the intermediate portion.

In some embodiments the length of at least one branch in theintermediate portion is between about 1 cm and about 5 cm.

In some embodiments the flexible branches conform to a radially outersurface of the portion of the medical device.

In some embodiments the branches of the intermediate portion conform tothe portion of the medical device such that they are oriented in aconfiguration surrounding a longitudinal axis of the medical device. Thebranches can extend substantially 360 degrees around the longitudinalaxis and at least two of the plurality of branches are separated by morethan 30 degrees from an adjacent branch. In some embodiments any twobranches are separated by more than 10 degrees. In some embodiments anytwo branches are separated by more than 90 degrees.

In some embodiments the plurality of branches of the intermediateportion are fixed on the medical device such that the medical devicemaintains the separation between the branches. The portion of themedical device can be an expandable membrane. The orientation of thebranches of the intermediate portion can depend on the inflation of theexpandable membrane. A portion of the expandable membrane and a portionof a plurality of the branches can be located distally to the distal endwhen the expandable membrane is in an expanded configuration.

In some embodiments at least two of the branches are comprised of aplurality of electrodes adapted to deliver radio frequency (RF) energy.The distal end can be comprised of a sensing electrode spaced apart fromthe plurality of electrodes.

In some embodiments the proximal end is coupled to a catheter. Thecatheter can be sealed along a length thereof extending from theproximal end to the intermediate portion.

In some embodiments at least three branches terminate in a connector atthe proximal end. In some embodiment portions of the medical device areadapted to be folded by selective orientation of the plurality ofbranches.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects will now be described in detail with referenceto the following drawings. Generally speaking the figures are not toscale in absolute terms or comparatively but are intended to beillustrative of claimed features. Also, relative placement of featuresand elements may be modified for the purpose of illustrative clarity.

FIGS. 1A-1B show enlarged, cross-sectional schematic views of anembodiment of an electrode assembly.

FIG. 1C illustrates an embodiment of a flex circuit for an electrodedevice.

FIG. 1D illustrates an embodiment of an electrode assembly including amembrane, flex circuit and electrodes.

FIGS. 2A-2E illustrate cross-sectional views of various embodiments ofan electrode assembly.

FIG. 2F illustrates a cross-sectional view of an existing flex circuit.

FIGS. 3A-3E illustrate top views of various embodiments of a flexcircuit.

FIGS. 4A-4C illustrate cross-sectional views of an embodiment of anelectrode assembly in different folding configurations.

FIGS. 5A-5I illustrate various exemplary electrode patterns andelectrode shapes.

FIGS. 6A-6B illustrate groupings of multiple smaller electrodes creatinga larger electrode.

FIG. 6C illustrates an embodiment of an electrode that includes a smallmapping electrode.

FIG. 6D illustrates an embodiment of an electrode configured as a dualspiral with the inner ends merged.

FIGS. 7A-7E illustrate various embodiments of electrodes and a flexcircuit having mapping electrodes and temperature sensors.

FIG. 8 illustrates an embodiment of the flex circuitry wiring.

FIGS. 9A-9B illustrate various electrode configurations and activationmechanisms.

FIG. 10 illustrates an embodiment of electrode activation using anelectrode sleeve.

FIG. 11 illustrates another embodiment of electrode activation using anelectrode sleeve.

FIG. 12 shows an embodiment of an electrode pattern that can be used forablation.

FIGS. 13A-13B illustrate embodiments of a flex circuit at theelectrodes.

FIGS. 14A-14B illustrate embodiments of an electrode assembly having acylindrical electrode element and an electrode sheath.

FIGS. 15A-15B illustrate embodiments of an electrode assembly having acylindrical electrode element within a sheath.

FIGS. 16A-16B illustrate embodiments of an electrode assembly having acylindrical electrode element.

FIGS. 17A-17G illustrate embodiments of an electrode assembly having anexpandable electrode structure.

FIGS. 18A-18S illustrate embodiments of an electrode assembly having anexpandable electrode structure.

FIGS. 19A-19F illustrate embodiments of an electrode assembly having anexpandable electrode structure that can be deployed asymmetricallyand/or can be of various shapes.

FIGS. 20A-20C illustrate embodiments of an electrode assembly having anexpandable electrode structure that can be deployed into various shapes.

FIGS. 21A-21E illustrate the tissue conformability of embodiments of theexpandable electrode structure.

FIGS. 22A-22C illustrate embodiments of electrode deposition onto adeployable membrane.

FIGS. 23A-23H illustrate embodiments of flex circuit routing through anelectrode device and electrode deposition onto a deployable membrane.

FIGS. 24A-24B illustrate folding of an embodiment of a deployablemembrane having flex circuits attached thereto.

FIGS. 25A-25C illustrate embodiments of a catheter having features toimprove flexibility and torque control.

FIGS. 26A-26C illustrate embodiments of a steerable catheter having amembrane mounted thereto.

FIGS. 27A-27C illustrate embodiments of a steerable catheter having amembrane mounted thereto and steerable elements mounted to the membrane.

FIGS. 28A-28F illustrate an embodiment of an expandable electrodestructure having mapping and ablation electrodes deposited thereon.

FIGS. 29A-29C illustrate embodiments of an electrode assembly integratedwith additional expandable structures that can be used for mappingand/or anchoring.

FIG. 30 illustrates an embodiment of an electrode assembly integratedwith a mapping catheter.

FIGS. 31A-31B illustrate an embodiment of a linear mapping electrodecatheter.

FIGS. 32A-32B illustrate an embodiment of a self-expanding mappingelectrode structure.

FIGS. 33A-33D illustrate embodiments of a mapping electrode structure.

FIGS. 34A-34F illustrate embodiments of a flex circuit that can be usedfor a mapping electrode structure.

FIG. 35 illustrates an embodiment of an electrode support structure.

FIGS. 36A-36B illustrate an embodiment of an electrode system for usenear a heat sink.

FIGS. 37A-37F illustrate embodiments of irrigation holes positioned nearone or more electrodes.

FIGS. 38A-38I illustrate embodiments of a visualization system for usewith an electrode assembly.

FIGS. 38J-38R illustrate exemplary optic structures and exemplaryexpandable membranes.

FIGS. 39A-39E illustrate various embodiments of radiopaque markersystems.

FIGS. 40A-40E illustrate various embodiments of radiopaque markersystems.

FIGS. 41A-41B illustrates embodiments for sensing tissue contact viaimpedance measurements.

FIGS. 41C-41D illustrate various embodiments of micro-switches that canbe used to activate electrodes.

FIG. 42 illustrates an embodiment of a tissue contact assessmentmechanism that can be incorporated into the electrode assembly.

FIG. 43 illustrates another embodiment of a tissue contact assessmentmechanism that can be incorporated into the electrode assembly.

FIGS. 44A-44F illustrate various embodiments of an anchoring system tocreate ablation lines.

FIGS. 45A-45B illustrate embodiments of an anchoring system for use withan electrode assembly.

FIGS. 46A-46B illustrate embodiments of a suction tip anchoring andelectrode assembly.

FIG. 47 illustrates an embodiment of a suction tip anchoring andelectrode assembly.

FIGS. 48A-48B illustrate an embodiment of a two arm suction tipanchoring and electrode assembly.

FIGS. 49A-49D illustrate an embodiment of a suction tip anchoring andelectrode assembly for creating continuous energy transmission lines.

FIG. 50 illustrates an embodiment of a suction anchoring and electrodeassembly.

FIGS. 51A-51C illustrate an embodiment of a suction anchoring andelectrode assembly for creating continuous energy transmission lines.

FIGS. 52A-52D illustrate an embodiment of an electrode system includingan inner suction catheter and an outer electrode catheter.

FIGS. 53A-53E illustrate an embodiment of a suction electrode catheterhaving an expandable region.

FIGS. 54A-54D illustrate an embodiment of a suction electrode catheterhaving more than one expandable region.

FIGS. 55A-55C illustrate an embodiment of a suction electrode catheterhaving more than one expandable region.

FIGS. 56A-56E illustrate various embodiments of a rapid exchangeelectrode sheath and anchoring catheter.

FIGS. 57A-57C illustrate a sheathing device that can be used to sheathan electrode assembly for minimally-invasive delivery.

FIGS. 58A-58K illustrate a method of sheathing the electrode assemblyfor minimally-invasive delivery.

FIG. 59 illustrates a device that can be used to assemble the electrodeassembly.

FIG. 60A-60D illustrate a flexible membrane incorporating electrodesdisposed around an expandable structure.

FIG. 61A-61C illustrates two embodiments of an electrode supportingmembrane and shaft interface.

FIG. 62A-62B illustrates an alternate embodiment of an electrodesupporting membrane and shaft interface.

FIG. 63A-63C illustrates an alternate embodiment of an electrodesupporting membrane and shaft interface.

FIG. 64 illustrates a system for using an electrode assembly.

FIG. 65 illustrates a sheathing device.

FIG. 66 illustrates a means of fabricating an electrode.

FIGS. 67A-67B illustrate arrangements of RFG electrode interfacing.

DETAILED DESCRIPTION

The use of minimally-invasive electrode devices, especially those foruse in regions of the body having somewhat complicated 3-D anatomy, hasbeen hindered by the conformability, flexibility and overall profile ofthe device as well as the electrode stimulation, ablation, mappingeffectiveness. Disclosed herein are devices having electrode assembliesthat incorporate one or more flexible electrodes deposited over one ormore flex circuits positioned on a deployable, flexible membrane. Theflexible electrodes can be used to sense, map, ablate, or stimulatemuscles and/or nerves. Energy transmission through the electrodes can beaccomplished over large surfaces such as the lining within an organ orselective regions for treatment of tumors, for example. Stimulation ofmuscles and/or nerves can be used to trigger signals to the brain ordirectly to a specified muscle cell/group. The electrode assemblies canalso be used as temporary implants for the purpose of providing orgenerating thermal energy for a specified period of time, such as can beneeded for stimulation of nerves and/or muscles. It should beappreciated that the electrodes and electrode assemblies describedherein can be used for a variety of functions as is known in the art,including but not limited to, ablation, mapping, sensing, and/orstimulating a variety of cells types and tissue types. When an electrodeis described herein to perform a particular function, such as ablation,it should not be construed to mean the electrode is incapable ofperforming another electrode function such as mapping, sensing orstimulating.

The electrode assemblies described herein are readily conformable,foldable and have a very low profile for minimally-invasive proceduresas well as a large overall surface area. The electrode assembliesdescribed herein allow for superior apposition to the target site andlimit the number of catheter manipulations required. Further, theelectrode assemblies described herein can greatly reduced proceduretimes and reduce the necessary skill level required to achievesuccessful results.

Although the devices, assemblies and methods of the present disclosureare at times described in terms of mapping, ablating or sensing tissuewhich creates aberrant electrical signals in the heart, it should beappreciated that the devices described herein can be used to treat avariety of conditions through sensing, mapping, ablation and/orstimulation in a variety of anatomical locations and that otherindications are considered herein. The devices, assemblies and methodsdescribed herein are not limited to treating cardiac conditions or anyother particular indication and can be used for any treatment in whichan energy delivery system is indicated, and in particular, aminimally-invasive treatment.

FIGS. 1A-1B show enlarged, cross-sectional schematic views of anembodiment of an electrode assembly 105. The electrode assembly 105 caninclude a flexible membrane 34, one or more flex circuits 89 and one ormore electrodes 6. The flex circuit 89 can include a base substrate 52,a conducting layer 96 and a dielectric layer 100. As shown in FIG. 1C,the flex circuit 89 can diverge from one or more main branches 17 intomultiple distal branches 87, each having one or more conductive traces16 (not shown) which each lead to one or more conductive pads 59 (notshown). The flex circuit 89 as shown in FIG. 1C can be wrapped around anexpandable membrane, such as a balloon (see FIG. 23G or 23H), so thatthe main branches 17 come together at the shaft. In an embodiment, eachconductive trace 16 can include at least two conductive pads 59. Theconductive pad 59 can be a region of the conductive trace 16 that has anexposed, non-insulated portion of the conducting layer 96. The electrode6 can be electrically coupled to the flex circuit 89 via the conductivepad 59 (not shown) of the conductive layer 96. The base substrate 52 canalso have a wider surface for better adhesion of the flex circuit 89 tothe membrane 34. With a larger base substrate surface, the conductivepad 59 can have a larger surface to electrically connect to theelectrode 6. It should be appreciated that the embodiment of theelectrode assembly shown in FIGS. 1A-1C is exemplary and that variationsin the structure, shape, and relative positions of the components arepossible.

Each electrode 6 can be a thin, electro-conductive film that covers atleast a portion of the flex circuit 89 and a portion of the outersurface of the membrane 34. FIG. 1D illustrates a portion of a membrane34 supporting a one distal branch of the flex circuit 87. The figureshows two electrodes 6 that overlap separate conductive pads 59 of theflex circuit 89, the corresponding conductive traces 16, and a portionof the flex circuit distal branch 87. The electrode 6 can have a surfacearea or diameter that is significantly larger than the conductive pad59. Because the electrode 6 has a larger surface area it also covers aportion of the membrane 34 not covered by the conductive pad 59 or theflex circuit distal branch 87.

The electrode assembly 105 can be deployed to deliver energy to a targettissue. When deployed, each electrode 6 on the membrane 34, both aloneand in combination, can cover a relatively large surface area of themembrane 34 with which to contact target tissues. Despite the largeoverall surface area of the electrodes 6 and the components of the flexcircuit 89 covering the flexible membrane 34, the electrode assembly 105can be compactly folded into a small diameter such that the electrodeassembly 105 can be delivered, for example, through small accesschannels for minimally-invasive delivery.

Flexible Electronics

The electrode devices described herein incorporate flexible electronicsthat are foldable to a very low profile for minimally-invasive deliveryin contrast to a relatively stiff and bulky electrode assembly. Uponreaching the target tissue, the electrode devices described herein canunfold to reveal a very large surface area electrode assembly that canbe readily conformable with the target tissues.

Flex Circuit

As mentioned above, the electrode assembly 105 of the devices describedherein can include one or more branching flex circuits 89. The flexcircuit 89 can include a base substrate 52, a conducting layer 96 and adielectric layer 100 as will be discussed in more detail below. Stillwith respect to FIG. 1D, the flex circuit 89 can include one or moremain proximal branches 17 (not shown) that can divide into multipleconductive distal branches 87. Each distal branch can contain multipleconductive traces 16, each having one or more conductive pads 59. Theconductive pad 59 has an electrically-conductive region formed byexposure of the conducting layer 96 upon removal of a portion of theoverlying insulating dielectric layer 100. The exposed portion ofconductive layer 96 can contact the conductive film electrode 6. Theconductive pad 59 can be a region of the conductive trace 16 that has alarger surface area due to a larger base substrate layer 52 andinsulating dielectric layer 100 (not shown). The method of conductivetrace 16 termination is created as known in the art. These regions ofwider and larger surface areas can be used for better adherence to themembrane.

As shown in FIG. 1C, the distal branches 87 of the flex circuit 89 canform a pattern of distal branches 87 that can spread out across themembrane 34. The branching pattern can vary and includes a fractal,self-repeating pattern or other symmetrical pattern, as well as anunsymmetrical pattern. The flex circuit 89 can include branches that aresinusoidal in shape so that some elongations between electrodes can beachieved. Multiple flex circuits 89 can be used to accommodate for thequantity and location of the multiple electrodes 6. Some elements of theflex circuitry 89 can have bridging elements 88 that facilitate handlingduring manufacturing (see FIG. 3C).

As shown in FIGS. 2A-2E, the flex circuit 89 and multiple conductivetraces 16 can be constructed using laminations of various materials, butgenerally includes a base substrate 52, an electrically conductive layer96 and an electrically insulating layer 100. In an embodiment, themultiple conductive traces 16 include a bottom insulating substratelayer 52, a middle conductive layer 96 and a top insulating dielectriclayer 100. The dielectric or top insulating layer 100 can be removed asis known in the art to expose a small region of the conductive layer 96.For example, a laser can be used to remove the dielectric layer 100 byetching as will be discussed in more detail below. In other embodiments,an adhesive layer can be used between the layers described above. Inother embodiments, multiple layers of conductivity and/or dielectricand/or adhesive can be included.

The materials used in the laminations of the flex circuit 89 can vary.The base substrate layer 52 and the electrically insulating layer 100can be a material such as, but not limited to, a thin flexible plasticsubstrate, polyimide, polyester, PET (polyethylene terephthalate), PEEK(polyaryletheretherketone), PTFE (polytetrafluoroethylene), PEN(polyethylene naphthalate), LCP (liquid crystal polymer), PIC(photoimageable coverlay), thin epoxy glass, polyimide glass, acrylicadhesive or other material. In an embodiment, the substrate or bottominsulating layer 52 and the dielectric or top insulating layer 100 canbe the same materials. In another embodiment, the substrate and thedielectric layers are different materials. For example, the substratecan be polyimide and the dielectric can be polyimide glass or similarmaterial.

The conductor or conductive layer 96 can be a material such as, but notlimited to, a metal or metal foil of copper, gold, silver, tin, nickel,steel, cupronickel (copper-nickel alloy), KOVAR (nickel-cobalt ferrousalloy) or other material. In an embodiment, more than one conductivematerial can be used in the conductive layer 96. In an embodiment, aconductive layer 96 of copper can be plated with a thin layer of anadditional conductive material at the conductive pad 59. In anembodiment, the thin layer of additional conductive material can begold. The flex circuit and its components can be manufactured usingtechniques as known in the art.

Still with respect to FIGS. 2A-2E, the flex circuit 89 and associatedconductive traces 16 and conductive pads 59 can be coupled to themembrane 34 by a variety of techniques known in the art to affix ametallic or polymer, shaped member onto another surface as are known inthe art. For example, an adhesive film 95 or other material can be usedto adhere the bottom layer of the flex circuit 89 to the membrane 34 aswill be discussed in more detail below. The adhesive film 95 can beconductive or non-conductive. For example, an adhesive 95 that isconductive can be laid over portions of the electrodes to adhere to theexposed conductive layer 96. Adhesive 95 that is not conductive can beused to bond the rest of the components to the membrane 34, for exampleto secure an end region of the flex circuit 89 to the membrane 34. Theflex circuit 89 can be direct formed into the membrane 34 as will bediscussed in detail below. Alternatively the conductive layer may beplated directly onto the substrate without the use of an interveninglayer of adhesive.

Although the conductive layer 96 can be relatively narrow, it can alsohave a surface that is somewhat planar, as opposed to having acylindrical geometry. The planar surface of the conductive layer 96 canhave a width and thickness that is optimized for carrying current to theelectrodes 6. Further, the plurality of conductive traces 16 can begrouped to create a planar surface width optimized to bond the flexcircuit 89 to the membrane 34. The flex circuit 89 can also include oneor more holes 53 incorporated through the base substrate 52 and theinsulating layer 100 to allow for adhesive to wick through to improveadhesion of the flex circuit 89 to the membrane 34 (see FIG. 1D).

FIGS. 2A-2E illustrate various lamination configurations of the flexcircuit and electrode assembly 105. The lamination configurations areexemplary and variations are possible. FIG. 2A shows an adhesive layer95 that is electrically non-conductive adjacent to the electrode 6 andcovers a portion of the membrane 34 and the flex circuit distal branch89. The conductive section of the conductive layer 96 contacts theelectrode 6. An adhesive layer 95 can also be applied over the top ofthe flex circuit distal branch 87 near an end where it contacts theelectrode 6 to secure the end of the distal branch 87 to the membrane34. The adhesive applied over this portion can be conductive to increasethe surface area of the electrode 6. In other embodiments, the electrode6 itself can also serve as an adhesive for portions of the flex circuit89 when conductivity is desired.

FIG. 2B shows a conductive trace 16 bonded to a membrane 34 using anadhesive 95. An exposed portion of the conductive layer 96, such aswhere the insulating layer 100 has been removed, can face away from themembrane 34 surface such that it does not come in direct contact withthe membrane 34. Since the conductive layer 96 faces away from themembrane 34, a non-conductive adhesive can be applied. The electrode 6covers the exposed portion of the conductive layer 96 as well as aportion of the membrane 34 and flex circuit distal branch 87. FIG. 2Cshows the distal branch 87 of a flex circuit 89 that is adhered to aregion of an inner surface of the membrane 34 as well as the outersurface of the membrane 34. The flex circuit distal branch 87 piercesthrough the membrane surface. In an embodiment, an adhesive layer 95 isnot used to fix the flex circuit 89 to the inner surface of the membrane34. The adhesive in this case can be non-conductive as the conductivelayer 96 faces away from the membrane 34. FIGS. 2D-2E shows the distalbranches of flex circuit 89 directly coupled to a membrane structure 34.FIG. 2D shows a membrane 34 encapsulating of the base substrate 52 ofthe flex circuit 89. The exposed conductive layer 96 is covered by theelectrode 6 which also covers part of the membrane. FIG. 2E shows anelectrode 6 embedded within the membrane 34 and the conductive layer 96of the flex circuit 89 covering a portion of the electrode such that theelectrode 6 and exposed conductive layer 96 are in contact.

The flexible and thin components of the flex circuit 89 contribute tothe low profile and low bulk of the electrode assembly 105 such that itcan fold to a very small profile for minimally-invasive delivery. Theflex circuit 89 can be affixed to the membrane 34 such that the membrane34 and electrodes 6 undergo preferential folding, for example between oracross the flex circuits 89. The folding can occur in an organized,controlled and repetitive manner. The flex circuit 89 can aid in betterpacking as it straightens out during folding and encourages the membraneto do the same. FIG. 2F shows an embodiment of an existing flex circuitwith multiple layers of conductive, adhesive and dielectric layers.

FIGS. 3A-3B show two embodiments of a flex circuit that can be used topower the electrodes described herein. The embodiments of 3A and 3B areexemplary and are not intended to be limiting. FIG. 3A shows a flexcircuit 89 that includes an array of distal branches 87 extending from aproximal main flex circuit lead 17 toward the distal end. The distalbranches 87 can split forming a Y-junction. This allows the flex circuit89 to continue at various angles from the main flex circuit lead 17 andcan be used to wrap a membrane 34, for example an expandableballoon-shaped membrane, at different latitudes along the surface. Thedistal branch 87 which can contain multiple conductive traces 16 can beelectrically insulated through the length of the flex circuit 89 and theconductive layer 96 exposed at specific points on the flex circuit 89,for example at a conductive pad 59 surrounded by an area of enlargedwidth or diameter substrate layer 52 and dielectric 100 (not shown). Thesubstrate layers 52 are shown including holes 53 through the substrate52 and insulating dielectric layer 100 (not shown) to facilitateattachment with, for example an adhesive. The embodiment of the flexcircuit 89 illustrated in FIG. 3A can power four electrodes (not shown)via the four conductive pads 59. The embodiment is shown as includingtwo temperature sensors 90, but it should be appreciated that fewer ormore than two temperature sensors 90 can be included. It should beunderstood that the temperature sensor also requires a conductive pad 59for power. The conductive traces for the temperature sensors 90 can alsobe used to simultaneously power a mapping electrode (not shown). In anembodiment five flex circuits 89 can be used to power twenty ablationelectrodes, ten mapping electrodes and ten temperature sensors 90.

FIG. 3B shows a different embodiment of the flex circuit 89 in which allthe flex circuits are integrated into a single piece that can be splitinto all the distal branches 87 needed to power the electrodes 6. Theflex circuit 89 in this embodiment is a single unit that is split into anumber of branches. These branches 87 can be connected to one anothervia a small bridge 88 on the substrate at various points throughout thelength of the flex circuit 89 (see FIG. 3C). The flex circuit 89 can berolled up into a small profile to insert the flex circuit 89 into acatheter for assembly. Since the flex circuit 89 can be split intobranches 87, these cuts help facilitate the flexing and bendingnecessary for assembly and during use. The flex circuit 89 can be placedinside a catheter and at the distal end; each branch 87 can peel away atthe distal end to form a Y-junction as shown in FIG. 3A. The flexcircuit 89 can then be attached to the membrane 34 at the variousdesired positions. The flex circuit 89 can also include staggeredconductive pads 59. Staggering the position of the conductive pads 59can aid in providing a low profile to reduce a stack up of the regionsof enlarged width or diameter substrate 52. The distal end region of thebranches 87 can contain an extra amount of length to be used assacrificial tabs 102. These sacrificial tabs 102 can be used to providefor consistent tensioning of the flex circuit branches 87 duringassembly. The tabs 102 can be mounted to an assembly fixture (see FIG.59) to ensure the locations of each tab 102 and each branch 87 of theflex circuit 89 is properly positioned relative to the membrane 34and/or shaft 57.

FIG. 3D shows an alternate embodiment of the distal end of the flexcircuit shown in FIG. 3B. In this embodiment the branches 87 areseparated as in the flex circuit of FIG. 3B but, in contrast to theembodiment of FIG. 3B, are again remerged into a single length ofsubstrate, tab 116 (at the top in the figure), at the very distal end ofthe flex circuit. This tab 116 wraps the distal end around a shaft,thereby forming a ring structure at the distal end of the flex circuitthat may be locked in place. Incorporated in tab 116 is slot 117 intowhich the free section of tab 116 can be slipped and affixed, therebyforming a ring of substrate material. Also incorporated in the flexcircuit of FIG. 3D is an additional tab 116 and slot 117 at the proximalend of the branches (shown at the bottom of the figure). The sectionbetween the two attachment tabs 116 is the intermediate portion. In suchan embodiment the flex circuit may be affixed to the membrane 34 of anexpandable element continuously on the surface of membrane 34 or atmultiple points on membrane 34, or may be affixed only at the proximaland distal edges of the membrane 34. Such an embodiment can haveadvantages both in manufacturing and packing relative to delivery. Alsoshown in FIG. 3D are staggered conductive pads 59 a, 59 b, and 59 c.

The intermediate portion is comprised of a plurality of individualbranches separated from one another along their lengths, wherein atleast one branch has an insulating layer along a portion thereof and atleast one branch is electrically connected to an electrode adapted todeliver radio frequency energy. The plurality of branches, as shown, arecoupled to one another distal to the intermediate portion where they areseparated along their lengths.

FIG. 3E is an exemplary complete flex circuit element 89 viewed from thesubstrate side which incorporates the distal end of the flex circuit 89illustrated in FIG. 3D. Flex circuit 89 incorporates bends 118 whichfacilitate the manufacture of flex circuit 89. During assembly of theelectrode assembly, bends 118 are folded such that flex circuit 89 maybe wrapped around or within a shaft of the delivery system. In such afashion the flex circuit can span from the electrodes of the electrodeassembly to a connector at a handle (not shown) into which flex circuitinterface 119 is connected. A flex circuit of a length greater thanabout 12 inches can therefore be manufactured on a surface which is nogreater than about 12 inches in any dimension. In some instances it maybe desirable to create multiple segments of flex circuit 89 and connectthem as part of the catheter fabrication process. In such cases the flexcircuit may be segmented normal to primary direction of the conductors.Convenient locations for such segments to start and end are at the folds108, in which case the number of connections could replace a same numberof folds. The connections thus knit the segments into a unitarystructure. Alternatively the direction of segmentation can be parallelto the primary direction of the conductors, in which case the segmentswould travel the same length as the single structures previouslydescribed. Tabs 116 can be modified to interface between segments thusallowing the segments to be knit into a unitary structure.

In some embodiments the length of at least one branch in theintermediate portion is between about 1 cm and about 5 cm.

The circuit shown in FIG. 3E may alternatively be printed on a tubularsubstrate which is the full unfolded length of the circuit. In such anembodiment the tubing base substrate may be slotted in areas requiringexpansion or additional flexibility. Circuit printing techniques such asthose used in InkJet Flex circuits can be used in these embodiments.Alternatively, the circuit can be printed on one full length of thecircuit, eliminating the need for bends. If incorporated, the foldsallow for printing on more readily available fabrication equipment.

In some situations where the number of electrodes and ancillary sensorsis minimal the flex circuit may be replaced by wires affixed to theflexible membrane 34. FIG. 66 illustrates such an arrangement. In suchcases a wire lead which has been coined at its distal end to create athin section of sufficient flexibility and surface are to act as theelectrode of the flex circuit. Coined wire 145 can replace a flexcircuit branch 87. The coined wire 145 may be affixed to flexiblemembrane 34 using an adhesive film 95. The coined wire 145 may beaffixed over an electrode with a conductive adhesive as shown or may beaffixed with a non-conductive adhesive and the electrode fabricated overthe adhered coined wire 145 (not shown). The sensor leads can be treatedin the same fashion if required.

Electrodes

One or more electrodes 6 can contact specified non-insulated sections ofa conductive trace 16 of the flex circuit 89, the conductive pad 59, aswell as a portion of the deployable membrane 34 and insulated portion ofthe flex circuit 89. The electrodes 6 can be a thin film material thatcan be repeatedly folded such that the electrode 6 and membrane 34 canbe compacted into a small diameter for minimally-invasive delivery. Theconductive material of the electrode 6 has a relatively large surfacearea compared to the conductive pad 59 it contacts, which provides for alarge overall electrode area.

Despite this large surface area, the electrodes 6 do not significantlyincrease the stiffness of the membrane 34 and can fold with the membrane34. FIGS. 4A-4C show an embodiment of the interface bond where themembrane 34 is manufactured separately from the flex circuit 89 and theelectrode 6. The electrode 6 can be deposited such that it contactsspecified non-insulated section of the conductive layer 96 and a portionof the membrane 34. FIG. 4A shows a slight curvature in the membrane 34and how the electrode 6 can follow this curvature. FIG. 4B shows theelectrode 6 folded away from the membrane 34 whereas FIG. 4C shows theelectrode 6 folded inwards and possibly contacting itself. Despite thelarge surface area covered, the thin electrode 6 and the membrane 34 canstill be folded (see FIGS. 4B and 4C). The electrode 6 can fold and flexto substantially the same extent as the membrane 34, even a region ofthe membrane 34 not covered by an electrode layer, such that theelectrode 6 does not impede the flexibility of the membrane 34 or theelectrode assembly 105. It should be appreciated that the electrode 6can fold upon itself along with the membrane 34, although folding canalso occur between the electrodes 6. The ability to fold can allow for alower device profile.

The materials used to create the electrodes 6 can vary. The electrodes 6can be a thin film of an electro-conductive or optical ink. The ink canbe polymer-based for better adhesion to the membrane. The electrodematerial can be a biocompatible, low resistance metal such as silver,silver flake, gold, and platinum which are additionally radiopaque. Inksmay additionally comprise materials such as carbon and/or graphite incombination with the more conductive materials already described. Theaddition of carbon and/or graphite can increase the conductivity of thepolymer matrix. When incorporated as fibers the carbon and/or graphiteadd additional structural integrity to the ink electrode. Other fibermaterials may be substituted to attain the same end. When the electrodematerial is not particularly radiopaque, additives such as tantalum andtungsten may be blended with the electrode material to enhanceradiopacity. An example of an electro-conductive ink is provided byEngineered Conductive Materials, LLC (ECM) which is a polyurethane-basedsilver loaded ink. Another example is Creative Materials Inc., whichmanufactures conductive inks, films, as well as radiopaque inks. Asmentioned above, the electrodes 6 can be applied to the membrane 34 andflex circuit 89 using an adhesive. Alternatively, the electrode materialcan have adhesive properties or be an adhesive-loaded with conductiveparticles such as silver flakes such that the electrodes 6 can adherethe components of the flex circuit 89 to the membrane 34. If anadditional adhesive layer is used to adhere the electrode 6 to themembrane 34 and flex circuit 89, the adhesive layer can include aconductive or non-conductive material. The electrodes formed withelectro-conductive or optical ink or thin metal film can be visualizedunder fluoroscopy to provide a general sense of the shape of themembrane and location of the electrode. To enhance visualization underfluoroscopy, radiopaque additives can be included in the electrodematerial or radiopaque markers laid out next to, on top or below theelectrodes as will be discussed in more detail below.

The electrode material can be deposited using a variety of techniquesknown in the art including, but not limited to, printing, pad printing,screen printing, silk screening, flexography, gravure, offsetlithography, inkjet, painting, spraying, soldering, bonding depositedusing touch-less technologies or otherwise transferred onto the surfaceof the membrane 34. In an embodiment, the electrode 6 can be formed bydepositing an electrically conductive coating or layer by spraying adesignated surface region. Alternatively, the electrode can be formed bydepositing the electrically-conductive material onto a region of themembrane 34 by vacuum deposition or printing the electrically conductivematerial on the designated surface region. This provides an electricallyconductive coating of a desired thickness and a relatively uniformelectrode through the desired area. Printing processes can include padprinting, screen printing and the like. Touch-free technologies such aspositive material deposition of ink such as from a syringe or similardevice can also be used to transfer conductive film or ink onto themembrane or substrates that are sensitive to pressure.

The electrodes can also be made using thin, conductive adhesive film orgel that can be cut to the shape of the electrodes and serve as anadhesive for the flex circuit when conductivity is desired. Theconductive adhesive gel can be mixed with conductive particles forconductivity and disposed over the substrate and UV cured.

Each region of electrically conductive material can be deposited overand electrically connected to a specified conductive pad 59 of the flexcircuit 89 and coupled to the surface of the membrane 34. The electrodescan be formed by using a mask (chemical or mechanical) over the membraneduring the deposition process, which can deposit electrode material overthe membrane and the mask alike. Once the deposition process iscompleted, the masking can be removed as is known in the art. Analternate technique can be used where automated robotic systems areprogrammed to precisely and accurately spray only the desired electrodesurfaces without the presence of a mask. This technique can havemultiple movable axes such as the Engineering Fluid Dispensing Inc.dispensing robots (East Providence, R.I.).

The flex circuit 89 components can be bonded before, during or afterdeposition of the electrodes 6 to the membrane 34, for example, using anadhesive or thermal bond or the like as described above. Theelectrically conductive layer 96 of the flex circuit distal branches 87can be exposed by etching away a portion of the dielectric layer 100.

The shape and pattern of electrodes 6 created can vary. The surfacearea, shape and pattern of the electrodes 6 can influence the amount ofenergy applied and the ablation line created. FIGS. 5A-51 illustratevarious electrode patterns and electrode shapes considered hereinincluding, but not limited to, circular, rectangular, octagonal,polygonal etc. The shape and pattern of the electrodes 6 deposited onthe membrane 34 can be selected depending upon the intended applicationof the electrode assembly. A square electrode, for example, can bebetter suited for interpolation based on image projection analysis, suchas to reproduce the shape of deployable membrane 34 in a mapping andidentification software algorithm. One or more rows of electrodes 6 canbe used. Each row of electrodes 6 can have the same shape or can vary inshape and size. Spacing between the electrodes 6 within the same row orspacing between the rows can alter the depth and quality of lesioncreated. The rows of electrodes can have electrodes that line up or canbe staggered as shown in FIG. 5D. The electrodes 6 can be arranged inpatterns that wrap around the flexible membrane structure to providerings of electrodes as in FIGS. 5A-5F, or on “diagonals” such that whenwrapped the electrode pattern will form helices. Patterns of electrodesmay in addition be addressable by the RF power source individually as inFIG. 5G and others, or in groups as in FIGS. 5H and 5I. The electrodepattern may incorporate a single ring as illustrated in FIGS. 5A-5C, orthey may incorporate two rows as in FIGS. 5D-5F, or they may incorporatemore than two rows. The electrodes 6 can also be deposited in a varietyof other locations on the deployable membrane 34 as will be described inmore detail below.

Helical patterns of the electrodes have particular advantage when usedto create lesions in body lumens, for example the pulmonary veins. Insuch situations there is a risk that if the lesions were created as aring on a single plane normal to the long axis of the vessel or lumen,swelling of the lumen resulting from the ablative injury or thesubsequent healing might stenos at a ring lesion. By wrapping theelectrodes as indicated in FIGS. 18P and 18S the impact of any resultantstenosis associated with each lesion are not allowed to become additive.A single helical electrode energized in a monopolar fashion, or twohelical electrodes spaced apart, as in FIG. 5G, may have advantages withregard to simplicity of the RF source, speed of application, and minimalfabrication costs. These configurations, however, have limitations whenthe uniformity of lesion, and the ability to modify the lesion inresponse to feedback acquired from sensing electrodes, to be describedas described elsewhere herein, are primary to effective therapy.

With reference to the uniformity of lesion, as the electrode surfaceincreases the uniformity of tissue contact across the electrode can belessened. This variation can be minimized by using a flexible electrodeon a flexible membrane, also described elsewhere herein. However, as thesurface area of the electrode grows, and or the aspect ratio for of theelectrode increases, as in the long helical elements just described, theuniformity of contact become less controllable. As the contact areavaries the current gradients and possibly total current delivered,depending on system design, will vary. Since the amount, and spacialdistribution, of current transmitted to the tissue from the electrodecontrol the size and depth of the resultant lesion, it is often moreadvantageous to use multiple smaller individually addressableelectrodes. In addition to helical patterns of electrodes, rectilineararrays may be used where the helical lesion pattern is created byaddressing an appropriate pattern of electrodes, either individually orin pairs depending whether monopolar or bipolar energy is used. Nonehelical patterns will have similar advantage to those stated for thehelical pattern when their projection on a plane normal to the long axisof the lumen are continuous and closed, The spacing between electrodesis another important characteristic which can be used to control thevolume of the lesion. As such, although not pictured, the presentdescription anticipates various spacing and arrangements ofaddressability not specifically illustrated or described herein.

FIG. 12 shows an embodiment of a pattern of electrodes 6. The patternshown in FIG. 12 is exemplary and variations in the pattern arepossible. Current 92 can be passed between adjacent electrodes 6 and/oroverlap an electrode 6 to reach the next electrode 6 to create thedesired ablation line. Each of the electrodes 6 can be created as asolid pattern, a set of concentric circles or other geometric shape, ora set of lines intersecting or not. The surface area, shape and internalpattern of the electrodes can influence the density of the current andburn line created. These features can also affect the amount of currentand power required as well as duty cycle and/or pulse wave modulation.There can be more than one row of electrodes 6 to allow the user toactively select which region to use for creating the ablation lesion andavoid having to exactly position the device and or manipulate to createthe proper ablation line. The ablation line can be created in adesirable location using techniques that are easy and fast and withoutthe need for tedious repositioning.

The multiple electrodes 6 deposited on the membrane 34 can collectivelycreate a large electrode array of energy-transmitting elements. Thiselectrode array can form a variety of patterns across the membrane 34and has an energy-transmitting surface area. The electrode array patternand energy-transmitting surface area can vary. In an embodiment, theenergy-transmitting surface area covers at least about 10% of themembrane surface area to be selectively activated. In an embodiment, theenergy-transmitting surface area can cover about 25% of the membranesurface area. In another embodiment, the energy-transmitting surfacearea can cover approximately 50% of the membrane surface area. Theenergy-transmitting surface area can be a factor of the physical surfacearea of each individual electrode within the energy-transmitting arrayas well as the projection of the expected ablation surface area based onthe electrode pattern spacing. The preferred energy-transmitting surfacearea percentage can also vary depending upon the indication beingtreated. For example, for the treatment of atrial fibrillation theenergy-transmitting surface area can cover at least 25% of the membranesurface to be selectively activated. In another embodiment, theenergy-transmitting surface area can cover greater than 40% of themembrane surface to be selectively activated. These percentages areprovided for example and can vary. The large energy-transmitting surfacearea allows the membrane surface to selectively ablate more tissuesimultaneously without the need for repositioning. Generally, the lesionsite can be slightly larger than the energy-transmitting surface area.

Each electrode 6 can also be a grouping of multiple smaller electrodes51 such as the embodiments shown in FIGS. 6A-6B. Each of the smallerelectrodes 51 can be connected by the conductive traces 16 of the flexcircuit 89 as shown in FIG. 6B to form a larger electrode 6.Alternatively, the smaller electrodes 51 can be independently activatedfor mapping electrical signals as may be needed in some indications suchas the treatment of atrial fibrillation. The traces 16 can be created asa sinusoidal line, for example, to allow for some elongation of theexpandable element so that the individual electrodes can spread fartherapart and the electrodes become substantially larger. As shown in FIG.6B, traces 16 allow for uniform elongation in all directions.Alternatively, the traces 16 can allow for elongation in specifieddirections. The surface area, shape and pattern of the electrodes caninfluence the amount of energy transmitted to the target tissue.Measurement with smaller electrodes 51 can provide higher resolution andaccuracy of the signal location, which can be useful for example inmapping aberrant signals. FIG. 6C illustrates an embodiment of anelectrode 6 that includes a small electrode 51 located at the center ofthe larger electrode 6. Each of the electrodes is connected to theirindividual traces 16. This embodiment can be used to confirm conductionblock such as during treatment of atrial fibrillation by comparingconductivity before and after ablation or by moving the electrodestructure further into the pulmonary vein for measurements. FIG. 6Dillustrates an embodiment of an electrode 6 configured as a dual spiralwith the inner ends merged. This embodiment can be used when theresistance of the electrode is required to be monitored such as when theelectrode is used as a temperature sensor in conjunction with itselectrode function as discussed elsewhere herein. In such aconfiguration the long path of the trace forming the electrode iscontained in a small area. Arranging the electrode as a long path allowschanges in the resistance as different areas of the electrode havecomparable effects on the overall resistance of the electrode.

The electrode 6 can be a thin, flexible film that is deposited over aportion of the flex circuit 89 as well as a portion of the membrane 34.As discussed briefly above and shown as an example in FIGS. 7A-7E, eachof the electrodes 6 has dimensions that exceed those of the conductivepad 59 or the conductive trace 16 of the flex circuit 89 such that theelectrode 6 covers an area of the membrane 34 on which the flex circuit89 is mounted. FIG. 7A shows the substrate layer 52 of the flex circuit89 following and outlining the conductive traces 16. The electrodes 6can extend beyond the substrate layer 52 onto the underlying membrane 34to provide a large surface for the electrode 6 to contact the tissue.This is in contrast to many devices known in the art which use thesmall, non-insulated portion of the flex circuit itself as the electrodeelement. Larger surface area and bigger overall electrodes 6 allow theelectrode assembly 105 of the devices described herein to transmitenergy deeper and with less risk of gaps in the energy transmissionline. To increase the durability of the electrodes 6, the substratelayer 52 can be extended over portions of the electrodes 6. This canrestrict elongation on sections of the membrane where the electrodes 6are located and can ensure, for example predictable ablation lesion sizeand quality. FIG. 7B shows the substrate layer 52 can extend to outlinethe shape of the electrodes 6 to be deposited. FIG. 7C shows thesubstrate layer 52 can have finger-like extensions or struts that canextend to the edge of the electrodes 6. A combination of any of theabove can also be used.

The dimensions of the electrode 6 can vary. In an embodiment, eachelectrode 6 can be between about 0.015 to 0.050 mm in thickness. In anembodiment, each electrode 6 is less than 0.025 mm in thickness. In anembodiment, each electrode 6 can have an overall surface area of between3 and 36 mm2. In an embodiment, each electrode 6 can have a size that isapproximately about 2 mm round. In comparison, each conductive trace 16can be between about 0.05 mm and 0.10 mm in width and between about 0.02and 0.05 mm in thickness. Each conductive pad 59 can be between about0.05 and 0.70 mm in width and between about 0.02 and 0.05 mm inthickness. In an embodiment, each conductive pad 59 can have an overallsurface area of between about 0.002 and 0.450 mm2. In an embodiment, theconductive pad 59 can be approximately 0.5 mm round. It should beappreciated that the aforementioned dimensions are exemplary and thatvariations are possible.

The relative dimensions of the electrode 6 and portions of the flexcircuit 89, such as the conductive pad 59, can also vary. In anembodiment, the surface area of each electrode 6 as it relates to thesurface area of its associated conductive pad 59 can be described interms of a ratio and can be at least about 14:1. In another embodiment,the ratio of electrode width to conductor width can be about 13:1. Therelative dimensions between the electrode assembly components can alsovary depending upon the indication being treated. For example, atrialfibrillation-specific devices the ratio of surface area of electrode 6to surface area of conductive pad 59 can be at least about 44:1. Theconductive pad 59 can be approximately 0.5 mm round and the electrodecan be a minimum of approximately 3×3 mm or 3.4 mm round for a 44:1ratio. For an electrode having an area of 4 mm round, the ratio can beapproximately 62:1. For an electrode having an area of 5 mm round, theratio can be approximately 95:1. For an electrode having an area of 3×5mm, the ratio can be approximately 74:1. For an electrode having an areaof 5×5 mm, the ratio can be approximately 123:1. In another embodiment,the ratio of electrode width to conductor width on the flex circuit canbe approximately 35:1. The conductor width can be 0.07 mm and a minimumwidth of the electrode can be 3 mm for a 3×3 mm electrode. In anotherembodiment, the electrode can have a surface area of at least about 9mm² (3.4 mm round) and an electrical conductor of between about 0.025 to0.050 mm maximum thickness. This combination results in a flexibleelectrode that has a large surface area yet is connected to a very thinconductive trace. It should be appreciated that the aforementionedrelative dimensions are exemplary and that variations are possible.

The energy delivered by the electrodes 6 can vary. The energy caninclude direct current (DC), alternating current, radiofrequency (RF)energy, for example in a monopolar or bipolar energy configuration,microwave, high voltages. When using RF and or high voltages the energylevels can be adjusted to cause thermal damage by increasing the tissuetemperature to above 42° C. or by creating high voltage gradients tobring about irreversible electroporation (IRE). Microwave and RF energycan use the application of thermal energy for cell necrosis while IREcan use high voltage electrical pulses to create cell permeabilityleading to cell death. Voltage energy can be delivered in very highvoltage dosage in short bursts. Use of bipolar RF energy prevents thecurrent from traveling through the bloodstream and reduces the risk ofcharring and thrombus. Bipolar energy also removes the effect of bloodflow on the energy delivery compared to monopolar and generally providesmore consistent results. The electrode assembly 105 can be usedexclusively in the bipolar configuration without using the monopolarconfiguration to minimize or eliminate current transfer through thebloodstream. The energy applied during an energy transmission period canbe in the form of high energy and low energy cycles (on/off) oralternating high and low temperatures.

FIG. 8 illustrates an embodiment of the flex circuitry wiring for theelectrodes 6. Each electrode 6 can be connected to an RF amplifier 48.Each electrode 6 can be individually turned on and off for monopolar orbipolar energy transmission. For monopolar, the electrodes 6 can beconnected via a monopolar bus line 14 to a patient return electrode 13and can be individually or simultaneously activated by switches 37. Forbipolar, the electrodes 6 can be connected via a bipolar bus line 73 andcan be individually or simultaneously activated by switches 37.Variations in the manner of connection between the electrodes arepossible. As will be discussed in more detail below, temperature sensors90 can be included in the electrode assembly 105 and can share an RFconductive trace with an adjacent electrode 6. This allows for dual useof the conductors which reduces the overall bulk and profile of thedevice. It also eliminates the need for an additional assembly junctionon the membrane during manufacturing and allows for a narrower flexcircuit and lower profile. It should be appreciated that the electrodes6 can also be used for mapping as will be discussed in more detailbelow.

The electrodes 6 can include a variety of activation mechanisms.Multiple electrodes 6 can be individually connected to a single flexcircuit 89 and can be individually controlled and individually activatedfor a more precise energy transmission via an electronic control box.Alternatively, the electrodes 6 can have a physical movable activationmeans, such as a conductive wire, which can be electrically connected toan array of electrodes in series. FIGS. 9A-9B, for example, show aconductive trace 16 that can be a movable wire housed within a lumen 33.The trace 16 can contact individual electrodes 6 located in series andactivate them individually or in unison. This can allow a user to createa burn pattern precisely where needed without having to move themembrane 34 to a different position. FIG. 10 shows another embodiment ofa selective activation mechanism which includes an electrode sleeve 10.A conductive trace 16 can be advanced distally or withdrawn proximallywithin a lumen of the electrode sleeve 10. The distal end of theconductive trace 16 can have a region of exposed conductive layer 96covered by an electrode 6 that can selectively contact the tissue to beablated through the openings 32 of the electrode sleeve 10. Thisconfiguration can allow the user to position the electrode device onceand tune the position of the electrodes 6 with the least amount ofmanipulation. This minimizes the amount of risk of trauma and injury tothe patient as well as reduces the time of the procedure. FIG. 11 showsan embodiment in which the electrode sleeve 10 having movable traces 16is mounted to a surface of a membrane 34 such as a balloon.

The electrodes 6 described herein can have low thermal mass or inertiafor quick heating and quick heat dissipation. This low thermal massprovides a more consistent and predictable temperature and energydelivery as well as a more accurate measurement of temperature andbetter user control of the energy. One or more temperature sensors 90can be mounted directly on the flex circuit 89 adjacent or over theelectrodes 6 to provide feedback during use of tissue temperature suchthat power, current, duty cycle can be modulated and maintained within aspecified temperature or temperature range. The temperature sensors 90considered herein can include surface mount thermistors, thermocouplesor other resistance temperature detectors or platinum resistancethermometers. The temperature sensor 90 can be bonded to the conductivetrace 16, for example, with an adhesive.

The number and pattern of temperature sensors 90 included in each flexcircuit 89 can vary. FIG. 12 shows an embodiment of an electrode 6 andtemperature sensor 90 pattern where the temperature sensor is locatedbetween two electrodes 6, between four electrodes 6 or in contact withone electrode 6. FIGS. 13A-13B show other embodiments of an electrodeassembly including a distal branch 87 and branching conductive traces 16of a flex circuit 89 contacting multiple electrodes 6 and a temperaturesensor 90. Each electrode 6 can be connected to one conductive trace 16stemming from the distal branch 87. The temperature sensor 90 can sharethe conductive trace 16 with the electrode 6 and be positioned nearwhere the electrode 6 is touching the tissue. For example, a temperaturesensor 90 can have a common ground and each end can be connected to oneof the electrodes 6 and switched/multiplexed with RF power. The dualusage for the trace 16 between temperature sensors 90 and electrodes 6reduces the overall profile of the electrode assembly 105. Fewerconnections results in less material and less bulk of the device, betterpacking and ease of manufacture.

The electrodes may be configured to provide the temperature sensingfunction thereby replacing some or all of the temperature sensorsdescribed herein. Such configurations include using the inherenttemperature coefficient of resistance (“tempco”) of the electrode as ameans to characterize the electrode temperature. Conductive ink ECMCI-1036 configured as a 0.3 mil thick electrode demonstrates a lineartempco of 0.005 ohms/degree C. over the range of 30 to 60 degree C. Thisis very close to the 0.006 ohms/degree C. associated with silver. Copperor aluminum with temperature coefficients approximately 0.004ohms/degree C. coated with silver or gold to protect the electrode andimprove biocompatibility are additional material useful for suchtemperature sensing electrodes. Platinum with a tempco of approximately0.004 ohms/degree C. is yet another material useful for such purposes.These materials may be used in any of the other electrode configurationsdescribed herein. Alternatively the electrodes may be comprised as aconductive ink modified to have a nonlinear tempco within the desiredtemperature control range and exhibiting a large change in tempco at apredetermined control temperature with in this range. In suchconfigurations the size, shape, loading, and composition of theconductive particles and the matrix polymer may be adjusted to createsuch a transition. In particular, as the matrix expands at the rateassociated with its coefficient of thermal expansion, the overlap andcontact area between particles is abruptly reduced, thereby abruptlyincreasing the electrical resistance. In such configurations theelectrode can act as its own temperature regulator.

In configurations using the electrode as a temperature sensor the returnline associated with the separate temperature sensors may be used as areturn line for measuring the temperature of the electrode. The returnline can be gated in such a fashion that it is an open circuit whendelivering RF and a closed circuit during a measurement period.Alternatively the temperature sensor has a very nonlinear tempco withinthe control range; a return line is not required. In this situation theinherent increase in resistivity of the electrode when used as atemperature sensor, or that of an ancillary temperature sensor when inuse, may be used to limit the delivery of RF energy after a controltemperature maximum has been attained.

The location, distribution throughout the flex circuit 89 and number oftemperature sensors 90 incorporated with the electrode assembly 105 canvary. In an embodiment, the temperature sensors 90 can be adjacent,directly covering, or in between the electrodes 6. FIG. 7A shows atemperature sensor 90 located in between two electrodes 6. In anon-limiting example, the temperature sensor 90 can be generally lessthan 1 mm away from the electrode 6. The trace connected to thetemperature sensor 90 can be shared with the trace 16 for the adjacentelectrode 6. FIGS. 7D and 7E shows an embodiment of an electrodeassembly 105 where the temperature sensor 90 is located at the center ofan electrode 6 instead of between two electrodes. The temperature sensor90 may be electrically isolated from the electrode 6. One or moretemperature sensors 90 can be used per pair of electrodes 6. In anembodiment, at least 10 temperature sensors 90 can be included fortemperature control.

Deployable Membrane

The electrode assembly 105 also includes a deployable, flexible membrane34 to which the flex circuit 89 and electrodes 6 can be coupled. Whendeployed, the membrane 34 can deliver energy through the large surfacearea of the electrodes 6 to a target tissue. The deployed membrane 34and electrodes 6 can ablate tissue over a large zone or area in avariety of patterns, for example circumferential, curved and linearpatterns, as will be discussed in more detail below. Despite the largeoverall surface area of the membrane 34 covered by the electrodes 6 andthe flex circuit 89, the membrane 34 can be readily conformable to thetarget tissue to be ablated and also compactly folded into a smalldiameter such that the electrode assembly 105 can be delivered, forexample, through small access channels for minimally-invasive delivery.

The structure of the membrane 34 can vary including, but not limited toa membrane sheet, cylinder, tube, inflatable, expandable, or fillablestructure, such as a balloon, or braided mesh and the like. In anembodiment, the electrode assembly includes a deployable membrane thatis formed into a linear structure or a cylindrical tube such as acylindrical electrode element 34 as shown in FIGS. 16A-16B. Thecylindrical membrane 34 can have multiple electrodes 6 deposited alongits length in varying patterns. The membrane 34 can be steered andmanipulated, for example to ablate two anatomical regionssimultaneously. The membrane 34 can include sections of varyingflexibility and stiffness for the ability to steer. The distal end ofthe membrane 34 can be manipulated with a guidewire 40 for properplacement at or near the target tissue 80, for example into a vesselsuch as the pulmonary vein for the treatment of atrial fibrillation. Aregion of the membrane 34, for example a middle region, can be highlyflexible such that by pushing a handle (not shown) distally the middleregion of the membrane 34 can bend and be directed toward anotheranatomical region, for example such as inserted into an adjacent vessel(FIG. 16B). This can be useful, for example, when ablating a regionbetween the two pulmonary veins that can have highly irregular anatomythat is difficult to access. The membrane 34 can also be inflated orexpanded to contact the vessel wall 83 and anchor the device in place aswill be discussed in more detail below. The cylindrical electrodeelement 34, which is located on the electrode catheter 71, can beadvanced through a sheath 65, such as a transseptal sheath (see FIGS.15A-15B). The user can control the distal end of the electrode sheath 76via a pull tether 70 at the proximal end of the electrode catheter 76.Pull tether 70 can be concentric and housed within the electrodecatheter 76 in some portion more proximal than what would be protrudingfrom the transseptal sheath 65.

In one embodiment, the electrode catheter 71 can be housed within anelectrode sheath 76 as shown in FIGS. 14A-14B. In an embodiment, one ormore electrodes 6 can be positioned on an outer surface along the lengthof the electrode sheath 76. The electrode catheter 71 can be used inconjunction to electrode sheath 76 to transmit thermal energy inmultiple locations. In another embodiment, the electrode sheath 76 canslide over a steerable guide catheter 47 anchored in place, for exampleusing an anchoring basket 50 or a suction tip 18 at the end of ananchoring catheter 15 to anchor onto neighboring tissue such as themyocardium near the pulmonary vein 80. The steerable guide catheter 47can be used to position the electrode sheath 76 to produce the desiredtreatment lines 81. It should be appreciated that the electrode sheath76, the electrode catheter 71 and steerable guide catheter 47 can beincorporated into a single catheter configuration.

The membrane 34 of the electrode assembly 105 can have an expandablestructure (self-expanding or otherwise) that can place the electrodes infull contact with tissues. The membrane 34 of the electrode assembly 105can have an expandable structure that is closed or fluid-tight, such asa balloon or a cylindrical tube. The membrane 34 of the electrodeassembly 105 can also span or have an expandable structure that is open,such as a woven, braided, stent or basket-like expandable structure asshown in FIGS. 17A-17D. In an embodiment, the expandable structure 93can radially expand to an open state (self-expanding or user-operated).The expandable structure 93 can be surrounded by the electrode assembly105 such that the flexible, outer membrane 34, flex circuit 89 andelectrodes 6 are disposed thereon. The expandable structure 93 can beattached to a catheter 57 via distal support elements 44. In oneembodiment the flexible membrane 34 can surround the expandablestructure 93 while attached by sutures at the intersections of thedistal support elements 44 and the expandable structure 93. In anotherembodiment, the membrane 34 may be weaved through some or all the loopsof the expandable structure 93 while allowing sufficient material forelongation and movement of the expandable structure 93. The electrodes(not shown) can also be mounted over a single wire or over theintersection of wires or both. The expandable structure 93 can beflexible and conform to a variety of anatomical shapes. FIG. 17A showsthe expandable structure 93 in a relatively elongated state with a lowerprofile more suitable for insertion and removal through a small accesschannel or sheath. FIG. 17B shows the expandable structure 93 in itsfully expanded state that can be used or is suitable for energytransmission. A guidewire (not shown) can be used when ablating, forexample around the pulmonary vein. When the guidewire is retracted, thedistal end of the expandable structure 93 can be used to ablate tissue.FIGS. 17C and 17D show close-up views of an embodiment of the wovenloops of the expandable structure 93. The expandable structure 93 can bea shape memory material such as Nitinol.

In another embodiment, shown in FIGS. 17E-17G, a catheter 57 can haveone or more electrodes disposed on an expandable structure. Theconfiguration of the expandable element can vary including a flat wireor coil. Once deployed the diameter of the electrode 6 can be largerthan the diameter of the catheter body 57. This promotes optimum contactwith the tissue 83 to be ablated or mapped. Additionally, these “spring”electrodes can be constructed for self-adjustment within their range ofmovement to conform to a variety of anatomies. A pressure or movementsensitive mechanism can be incorporated at each electrode in order toprovide feedback to the user about tissue contact prior to deviceactivation. A flexible membrane 34 can also be placed over these springelements with the electrodes disposed on the membrane.

The flexible membrane 54 can be disposed around an expandable structure98 that is self-expanding such as a braid, coil or the like, as shown inFIGS. 60A-60D. Electrodes 6 may be arranged over the tubular thin walledmembrane 54. A sheath 31 can cover the electrodes and support structurefor a low profile delivery. Once inside the desired location, the sheathcan be pulled back, exposing the structure 98 and the electrodes 6. Themembrane 54 can be attached to one or both ends of the support structure98. An exemplary benefit of this approach is that the device does notocclude the anatomy during ablation. The structure is open through itslongitudinal length and thus allows for the flow of fluid or gas. Thiseliminates a concern especially when treating blood vessels. Themembrane can also include holes, slits, or ports which allow foradditional fluid or gas passage to minimally interfere with anatomicalflows.

FIGS. 60A and 60B show an embodiment of this design. The structure 98 isdirectly attached to the catheter shaft 57 which creates a funnel shapeat the junction of the shaft and the structure. This facilitatessheathing and unsheathing of the structure. FIG. 60C shows anotherembodiment in which a coupling element 60 connects the shaft 57 and thestructure 98, which allows for full expansion of the support structure98 at the distal and proximal end and thus fully expansion of theelectrode-carrying membrane 54. A depiction of the flow of blood isindicated with arrows in FIG. 60C. FIG. 60D illustrates a thin wallmembrane 54 with electrodes 6 supported by a coil support structure 98.This embodiment allows for a very small profile in that a coil can besheathed into an essentially linear structure. To prevent distortion ofthe electrodes, the membrane 54 in this particular embodiment may beattached at only the proximal end or otherwise contain compliantsections not directly affecting the electrodes during sheathing.

The electrode assembly can include a perfusion balloon and catheterconfiguration in which blood flow is not restricted by the presence ofthe device. The assembly can include a large inner lumen which allowsthe use of a guidewire and is large enough to also accommodate for flowof fluid, such as blood. FIG. 18G illustrates one such embodiment. Theflow of blood indicated by arrows can enter the guidewire lumen and exita hole 110 that can be located just proximal to the membrane 34 on theshaft 57.

The membrane 34 of the electrode assembly 105 can also have a closed,expandable structure, such as a balloon as shown in FIGS. 18A-18M. Themembrane 34 can have an expandable structure that is fluid-tight suchthat it can be filled with a liquid or gas to expand or inflate it. Themembrane can be expanded using a variety of techniques such as byfilling with a gas or liquid, such as saline, a radiopaque dye, coolingfluid, blood-safe gas and the like. The expandable structure can also beself-expanding. The membrane 34 can be covered by multiple electrodes 6and can be coupled near its proximal region to a distal end of acatheter 57. The distal and proximal regions of the membrane structure34 shown in FIGS. 18A-18C protrude outwards forming smaller domes, whichcan provide convenience for manufacturing. FIGS. 18D-18M illustrateother embodiments of an electrode assembly 105 where the membrane 34 hasa continuous smooth surface and no protrusions or domed regions at itsdistal and proximal end regions. The distal end of the membrane 34 canbe flat or as shown in FIGS. 18F and 18G drawn into itself creating aconcave surface at its distal end. The surface of the membrane can bethat portion of the membrane that is expandable upon introduction offluid and that typically expands from proximal and distal points ofattachment to the catheter body.

FIGS. 18I-18M show various views of an embodiment of the deployablemembrane 34 of the electrode assembly 105 that has a fluid-tightexpandable structure. The deployable membrane 34 can have multipleelectrodes 6 electrically connected via one or more flex circuits 89. Asshown in FIG. 18I, each flex circuit 89 can be routed through the shaft57 and can exit or emerge from the inner diameter of the membrane 34 ata distal end region and split into two at a Y-junction. This allows asingle flex circuit 89 to be positioned at different latitude positionson a membrane 34. FIG. 18J shows an embodiment of the conductive pad 59that can be used to electrically connect the electrodes 6. FIG. 18Kshows an embodiment of a mapping electrode 51 that is smaller and inbetween the larger electrodes 6. FIG. 18L shows an embodiment of thedistal end region of the membrane 34 that can be drawn into itselfcreating a concave surface.

The flex circuit shown and described with reference to FIG. 3E can beseen in FIGS. 18N and 18O incorporated into a deployed electrodeassembly at the end of a shaft 57. The circuit includes an intermediateportion with a plurality of branches separated along their lengths. Inthis embodiment branches 87 are equally spaced from adjacent branchesalong an equator defined by the toroid-shaped membrane 34 in theexpanded configuration shown. The branches are affixed in a uniformlydistributed fashion around the equator of the toroid-shaped membrane 34in the expanded configuration shown. The branches are flexible andconform to membrane 34. Three rings of electrodes 6 can be seen, asingle ring electrode at the distal end of the expandable memberinterfaced with conductive pad 59 c (shown in other embodiments herein),a ring of ten individual electrodes interfaced with conductive pads 59 b(shown in other embodiments herein), and an additional ten electrodesinterfaced with conductive pads 59 a (shown in other embodimentsherein). The device also includes thermistor elements 90 interposedbetween electrode elements interfaced with the conductive pads.

In FIGS. 18N and 18O, the branches are coupled to the membrane such thatthey conform to the membrane and are uniformly spaced from one anotherin the membrane's expanded configuration. In an end view of the expandeddevice (looking in the distal-to-proximal direction), at least twoadjacent branches define an angle greater than 30 degrees. In someembodiments at least two adjacent branches can be separated by more thanabout 10 degrees. In some embodiments at least two branches areseparated by more than about 90 degrees. In alternative embodiments thebranches are not uniformly spaced from one another, such that twobranches define a first angle and two branches define a second angle,wherein the first angle is different than the second angle.

The branches are flexible, allowing them to conform to the radiallyouter surface of the membrane in FIGS. 18N and 18O. The branches extendsubstantially 360 degrees around the longitudinal axis of the shaft andare uniformly spaced from one another.

In FIGS. 18N and 18O the plurality of branches of the intermediateportion are fixed on the expandable membrane and the membrane maintainsthe separation between the branches. The configuration of the expandablemembrane can at least partially define the angles between the branchesof the intermediate portion and/or the orientation of the branches onthe membrane.

In some embodiments at least three branches terminate in a connector atthe proximal end of the flexible circuit.

In the embodiment in FIGS. 18N and 18O portions of the branches arefolded by selective orientation on the flexible expandable membrane.

The flex circuit 89 can wrap around the membrane 34 to power theelectrodes as shown in FIG. 18J. The flex circuit 89 can extend to theproximal end of the membrane 34 and/or into the distal end of the shaft57 as shown in FIG. 18M. Extending the flex circuit to the joint wherethe shaft 57 and the membrane 34 meet can increase the robustness andease of manufacturing the electrode assembly 105. The flex circuit mainleads can be inserted within the inner diameter of the shaft and bondedin place. This can be beneficial for preventing de-lamination of theflex circuit main leads 17, such as during the sheathing process. Thesesections of the flex circuit 89 can power another set of electrodeslocated at or near the proximal end of the membrane 34. With atoroidal-shaped, closed membrane 34, the location of the electrodes 6face away from the distal portion of the membrane 34, such that theyface in a proximal direction towards the shaft 57 of the assembly 105.This configuration can be useful in reaching target tissues that arelocated directly through an access point, such as for example the septumonce a catheter crosses the septum to enter the left atrium.

The shape of the expandable membrane 34 can vary including, but notlimited to, cylindrical, spherical, toroid, doughnut-like, conical,branched, pronged and other geometries. As shown in FIGS. 18D-18M, theexpandable membrane 34 has a toroid shape. This shape provides forbetter maneuverability of the distal tip due to the relatively shortlongitudinal length of the structure. A cylindrical shaped expandablemembrane 34 incorporated in electrode assembly 105 is illustrated isillustrated in FIGS. 18P-18S. In FIG. 18P the distal branches 87 of flexcircuit 89 have a configuration similar to that illustrated in FIGS. 3Dand 3F, where the distal branches are longer to accommodate thecylindrical shaped expandable membrane 34. An alternative configurationto the longitudinally oriented distal branches 87 of flex circuit 89 isshown in FIG. 18S. In this configuration the distal branches are woundabout the cylindrically shaped expandable membrane 34. Note that in FIG.18S only the substrate layer of the flexible circuit 89 have beenillustrated, but all of the features associated with the other flexcircuits herein described can be incorporated in the flex circuit ofFIG. 18S. The electrode assembly of 18P can be populated such that anelectrode is associated with any combination of locations indicated bythe irrigation holes shown. Using such an electrode assembly, a numberof helical lesion patterns of different orientation and pitch can becreated specific to the particular luminal site under treatment, withoutthe need to reposition the electrode structure.

FIG. 18H illustrates the swiveling action the toroid shaped membranestructure can achieve. Because the longitudinal length of the membranestructure on the catheter shaft is relatively short, the membranestructure can move relative to the shaft without bending the shaft. Whenthe membrane structure is used in a semi-inflated state, this allows forgreater motion or swiveling of the membrane structure on the shaft.Further, a smaller membrane structure 34 can be used, which although itmay be subject to more frequent manipulation of the electrode assembly105 during the procedure it can allow for easier manipulation especiallyin smaller and/or tight anatomies. Electrode assemblies having smallmembrane structures 34, such as shown in FIGS. 22A to 22B and FIGS. 26Ato 26C, can be useful for touch-ups during the procedure or duringfollow-up procedures.

The deployable membrane 34 can have an expandable structure that issymmetrical such as shown in FIG. 19A. The electrodes 6 can be evenlydistributed across the membrane 34 where they can be connected to theirindividual conductive traces 16 stemming from the distal flex circuitbranches 87. The distal branches 87 connect to the main flex circuitleads 17 (not shown) which can be routed through the catheter 57 suchthat they can connect at a proximal region for example at a handle. Thedeployable membrane 34 can also have an asymmetrical configuration asshown in FIGS. 19B and 19C. An asymmetrical structure can reduce bulkand can allow for easier manipulation and positioning of electrodes.FIG. 19C shows the asymmetrical membrane structure conforming to tissue83 such as the pulmonary vein. In atrial fibrillation applications, forexample, the deployable membrane 34 having an asymmetrical structure caninvolve two or more different applications of energy and rotations ofthe membrane 34 to completely isolate the pulmonary vein. Theasymmetrical structure can allow for better rotation control andplacement of the electrodes 6 against the tissue 83.

The electrode assembly 105 can include an enclosed membrane 34 and canbe of any shape or form, one of which can be a cylindrical shapedballoon. The membrane 34 can further be shaped to maintain a curvedposition or include one or more pull wires. FIGS. 19D-19F showalternative embodiments for a membrane 34 for an ablation assembly 105including one that has a flat distal end surface and one that is moreconical. It should be appreciated that other variations of the membraneshape can be possible. The length of the membrane 34 can be shorter orlonger and the shape can be straight or contain any amount of curvature.The electrode assembly 105 can include a flex circuit 89 which powersone or more electrodes 6. The electrodes 6 can be laid out in anasymmetrical pattern of electrodes 6 on the inside of the curve versusthe outside of the curvature. The distal end of the membrane 34 can alsoinclude a single large electrode 6 as shown in FIG. 19F. Fiber opticscopes 38 can be included to the electrode assembly 105 as well as shownin FIG. 19D.

The shape of the membrane 34 can be changed or adjusted before, duringor after use. FIGS. 20A-20C show an embodiment of an electrode assembly105 having a deployable membrane 34 that can be expanded into a balloonshape. The deployable membrane 34 is coupled at an outer surface of itsproximal region to support arms 44 extending from the distal end of thesteerable catheter 57. The membrane is coupled at its distal region to ashaft 46 that extends through and translatable relative to the steerablecatheter 57. The shaft 46 can translate from a proximal position inwhich the membrane 34 is folded distal to the catheter 57 and shaft 46.The shaft 46 can also translate to a distal position in which themembrane 34 expands into an enlarged structure and exposes the mostdistal electrodes suitable for energy transmission as seen in FIG. 20B.The shape of the membrane 34 can be varied depending upon the positionof the shaft 46 relative to the catheter 57. For example, the membrane34 can have a fully rounded configuration as shown in FIG. 20B or adistally flattened configuration such as shown in FIG. 20A or a distallyconcave configuration as shown in FIG. 20C or anywhere in between. Thisallows for positioning and exposure of the electrodes as needed to fullycontact the target tissue.

The membrane 34 and electrode assembly 105 can conform tothree-dimensional anatomy for optimum tissue contact and energytransmission. Good apposition of the membrane allows for better contactof the electrodes 6 to the surface of the tissue. The membrane 34 havingan expandable structure as described above can be expanded to a varietyof conformations, shapes and have a range of diameters over a relativelylow range of pressures. In an embodiment the membrane can be radiallyexpanded such that it fits and conforms within two regions of theanatomy simultaneously (for example see FIG. 16B). In anotherembodiment, the membrane 34 can have a large distal diameter (forexample FIGS. 18A-18M) and/or can be tapered, or funnel-shaped (forexample FIGS. 20A-20C). This allows for a better conformation tocircumferential geometries, for example regions near the ostia of apulmonary vein.

FIGS. 21A-21E illustrate how a membrane 34 having an expandableballoon-type structure can conform to tissue 83 having a variety ofanatomical shapes. The membrane 34 can be semi- or non-compliant, butcan still conform to target tissues depending the degree to which it isfilled. In an embodiment, the deployable membrane 34 can benon-compliant and have an expandable, closed structure that is onlypartially filled. Partial filling of a non-compliant, closed structurecan allow it to properly conform to the target tissue despite thenon-compliant properties of the membrane material itself. In anotherembodiment, the deployable membrane 34 has an expandable, closedstructure and a relatively short longitudinal length. In thisembodiment, partial filling of the structure such as with a fluid, gasor liquid results in a conformability and swiveling steerability. Themembrane 34 can have an expandable, closed structure that is branched orcan split into two branches at its distal end upon expansion. In theexpanded state, electrodes 6 on each of the branches can be in contactwith the tissue 83 during energy transmission (see FIG. 21E). Thepronged or two-leg shape can aid in reaching irregular surfaces between,for example two vessels such as the carina between the pulmonary vein80.

As described above, the electrodes 6 can be deposited on the membrane 34as well as on a portion of the flex circuit 89. The membrane 34 caninclude multiple electrodes 6 or the membrane 34 can have a singleelectrode 6 covering a portion or the entire membrane 34. For example,FIG. 22A shows a membrane 34 having multiple electrodes 6. FIG. 22Bshows a single electrode 6 covering a distal portion of the membrane 34.FIG. 22C shows a single electrode 6 that surrounds the entire outersurface of the membrane 34. Further, the membrane 34 can be impregnatedwith conductive material which then can become the electrode. It shouldbe appreciated that the size of the membrane 34, in particular anenclosed membrane such as the balloon shape shown in FIGS. 22A-22C, canbe of any size and shape. A small balloon size can be used for treatmentof small anatomical sites or for touch-up/follow-up secondarytreatments.

In addition to the variation in the number of electrodes 6 deposited onthe membrane 34, the location and pattern of electrode deposition canvary as well. For example, as shown in FIGS. 18A-18C the electrodes 6can be positioned on a section of the membrane structure 34 having thelargest diameter upon expansion. The distal domed region can includeelectrodes 6 for the purpose of mapping, sensing, stimulating and/orablation. FIGS. 18D-18M illustrate other embodiments of the membrane 34having electrodes 6 positioned circumferentially from the largestdiameter section of the membrane structure 34 to the flat region at thedistal end. As another example, in the treatment of atrial fibrillationthe electrodes can be positioned on the membrane structure to optimizecontact with the antrum of the ostium. The electrodes 6 can also beplaced at the proximal end of the membrane 34 as shown in FIG. 18M toablate or map structures in anatomical locations such as the septum asdescribed above.

The materials of the membranes 34 described herein can vary. Generally,the membrane material is thin, readily foldable into a low profile andrefoldable after expansion. The materials can be elastic, inelastic,stretchy, non-stretchy, compliant, semi-compliant, or non-compliant. Inan embodiment, the membrane 34 has an expandable structure and can beconstructed of materials such as those materials used in theconstruction of balloon catheters known in the art, including, but notlimited to polyvinyl chloride (PVC), polyethylene (PE), cross-linkedpolyethylene, polyolefins, polyolefin copolymer (POC), polyethyleneterephthalate (PET), nylon, polymer blends, polyester, polyimide,polyamides, polyurethane, silicone, polydimethylsiloxane (PDMS) and thelike. The membrane 34 can be constructed of relatively inelasticpolymers such as PE, POC, PET, polyimide or a nylon material. Themembrane 34 can be constructed of relatively compliant, elastomericmaterials including, but not limited to, a silicone, latex, urethanes,or Mylar elastomers. The membrane 34 can be embedded with othermaterials such as for example, metal, Kevlar or nylon fibers. Themembrane 34 can be constructed of a thin, non-extensible polymer filmsuch as polyester or other flexible thermoplastic or thermosettingpolymer film. In one embodiment the flexible membrane 34 can be 0.001″to 0.002″ in thickness to provide sufficient burst strength and allowfor foldability. In some embodiments it is preferable to have theelectrode mechanical properties as close to the membrane mechanicalproperties as possible. One way of providing this is to use an inelasticmembrane that will not stretch as it is expanded. This helps secure thebranches to the membrane.

Low Profile Folding and Delivery Conformation

The electrode assemblies and devices described herein incorporate adesign and structure that are optimized for low bulk and low profilefolding. The electrode assemblies and devices described herein can beused, for example in minimally-invasive delivery of energy transmissionto tissues. The construction of the electrode devices, such as therouting of the flex circuit main leads through the device, also cancontribute to the low bulk and low profile of the device.

A deployable membrane 34 having an expandable structure can be mountedat a distal end of a catheter 57 configured for percutaneous delivery(see FIGS. 23A-23H). The flex circuit main leads 17 of the flex circuit89 can extend from a handle (not shown) and be routed through an innerlumen of the catheter 57. The flex circuit main leads 17 can emerge outof the inner lumen of the catheter 57 as well as the inner diameter ofthe deployable membrane 34 at a distal end region as shown in FIGS. 23Aand 23B. Alternatively, the flex circuit main leads 17 can emerge from aproximal end region as shown in FIG. 23C-23H. The flex circuit mainleads 17 can be kept together until they emerge out of the catheter 57where they may branch out into their respective distal branches 87. Thedistal branches 87 can immediately branch out into multiple conductivetraces 16, which can be attached to an outer surface of the membrane 34.Other configurations of the flex circuit main leads 17 and distalbranches 87 are possible, the distal branch 87 can continue to thedistal tip of the balloon for example.

During manufacturing, the membrane 34 can be mounted on a temporarymandrel support having inflation ports to maintain a constant expandedstate during assembly. The flex circuit can have branches withsacrificial tabs 102 (see FIGS. 3A and 3B) that can be mated to anassembly fixture for consistent tensioning of all branches of the flexcircuit 89 during assembly. Adhesive can be applied to the inner surfaceof the flex circuit that will be in contact with the membrane 34. Thiscan be accomplished through the use of a robotic system that can applyprecise volume of adhesive and precise locations on the flex circuit.The main leads 17 of the flex circuit 89 can exit at or near the distalend of the shaft 57 or the proximal end of the flexible membrane 34 andextend distally (see FIGS. 23C-23H). Electrodes 6 can be positioned ator near the distal end of the membrane 34. They can be positioned as twodistal-most electrodes for each branch of the flex circuit as shown inFIGS. 23G-23H. It should be appreciated that the flex circuit 89 and theelectrodes 6 can vary in the power configuration and layout. Forexample, the end of each flex circuit 89 can terminate with one largeelectrode 6 instead of two smaller electrodes 6.

Folding of the deployable membrane 34 can occur distal to the end of thecatheter 57. A shaft 46 (see FIGS. 20A-20C) can be withdrawn in aproximal direction to fold the membrane 34 distal to the end of theshaft 46 and catheter 57. The folds of the membrane 34 do not thereforecontribute to bulk and overall diameter of the catheter 57.Alternatively, in other embodiments and membrane shapes, the shaft 46can be extended fully distally while elongating the membrane 34 (inparticular an elastic membrane) to minimize bunching of the membranematerial. An outer sheath (not shown) can additionally be used to coverthe folded up membrane 34 providing the electrode assembly 105 with asmooth outer surface for better delivery, for example through thevasculature. The deployable membrane 34, electrodes 6 and flex circuits89 can all fold up such that they fit inside a specified sheath sizeappropriate for the anatomical site to the treated. This allows for asmaller diameter of catheter shaft and, in turn, a very low profiledelivery configuration of the device, which minimizes the trauma andrisk of complications.

As shown in FIGS. 24A-24B, the membrane 34 can fold preferentially, forexample along, between or across the flex circuits 89 and electrodes 6when deflated or in the unexpanded state. The folding can occur in anorganized, controlled, predictable and repetitive manner. The flexcircuit 89 can also act to influence folding along a preferentialfolding line and provide for or aid in better packing of the electrodeassembly into a low profile delivery configuration.

Catheter

As described above, the electrode assemblies described herein can bemounted onto a catheter configured for percutaneous delivery. Control ofthe movement of catheters in general can be somewhat difficult due tothe elongated, tubular structure. To provide sufficient control over themovement, the catheters described herein can be somewhat rigid, but notso rigid as to prevent navigation of the catheter through the body toarrive at a precise location. Further, the catheter should not be sorigid that it could cause damage to portions of the body being treatedor through which it is passed. The catheters described herein can bemanufactured of a variety of materials known in the art of percutaneouscatheters including extruded polyether block amid (PEBAX) or otherpolymeric materials such as polyurethane, polycarbonate, nylon, FEP,PTFE, LDPE, and HDPE. The catheters described herein can be reinforcedas known in the art such as with a braided or coiled layer of stainlesssteel to increase torsional rigidity. Other reinforcement materials andconstructions can be used both metallic and polymer based. The catheterscan also be formed to a desired shape, such as a curved tip, for ease ofplacement into the proper orientation. One typical method of shaping acatheter is through thermal re-forming of an extruded catheter which canbe done pre- or post-assembly of the catheter. The catheter needs to beof sufficient length and adequate diameter to reach the target tissuethrough known access points without causing trauma to the tissue duringintroduction and tracking through the anatomy.

The catheters described herein can include a laser cut region 3 in avariety of patterns, such as an interlocking zigzag pattern or similar,to optimize flexibility while resisting compression and tension (seeFIG. 25A). FIG. 25B shows a close-up of a laser cut region 3 havingteeth lined up at every row. FIG. 25C shows a close-up of a laser cutregion 3 of the catheter having teeth lined up at every other row. Thispattern can be more resistant to tension or compression compared to thepattern of FIG. 25B. This laser cut region 3 can be added to any of thecatheters described herein such as the guide catheter or electrodecatheter or other catheter to increase the ease of use and improvemanipulation of the electrode assembly 105. The laser cut region 3 canbe constructed of metallic or polymeric material and an addition to thecatheter or part of the catheter structure.

The catheters described herein can be steerable in multiple directionsand can be held at various degrees of bend during the procedure as shownin FIG. 26A-26C. Generally steerable shafts or sheaths allow for motionat the distal end of the catheter itself. External elements distal tothe shaft or sheath tip can move indirectly. Furthermore, a steerableshaft located within a steerable sheath can result in a loss of functionas the shaft is constrained within the sheath. Embodiments describedherein allow for steering of the distal most element of the shaft, forexample a membrane attached to the shaft.

In an embodiment, the support arms 44 can be used to aid in maneuveringthe catheter shaft 57 in a distal and proximal direction. As shown inFIGS. 20A-20C, the membrane 34 was coupled to the catheter shaft 57using one or more support elements 44 extending from the distal end ofthe catheter 57 to provide better control of positioning and orientationof the electrode assembly 105 against the tissue. The support elements44 can be a shape memory material such as Nitinol and can haveradiopaque visual orientation markers 49 in the form of a specific shapeor element on the support elements 44 or the materials may in themselvesbe radiopaque. These can be used to identify the orientation of thedevice as will be described in more detail below.

FIGS. 27A-27C show various embodiments of a steerable or deflectablecatheter 57 having a membrane 34 mounted on its distal end. Theembodiments of FIGS. 27A-27C are examples and other embodiments arepossible. Steering elements 56 can be placed on the membrane 34 to allowfor precise control and placement of the membrane 34. These elements 56can be attached to the membrane 34, directly or indirectly, anywheredistal to the junction of the membrane 34 and catheter shaft 57. The useof the steering elements 56 allows for easier use of the deviceespecially in more tortuous anatomies. The elements 56 can be used in apulling configuration and/or have the ability to push. The ability tosteer at the membrane 34 eliminates any constriction an outer sheath ora traditional steerable shaft (not shown) may have on the full range ofmotion. The ability to steer distal to the junction enhances the overallmaneuverability of the device. Multiple steering elements 56 spacedequally or not can be used to allow for the desired degree ofmaneuverability. FIGS. 27A and 27B show the use of three steeringelements 56. In an embodiment, when one of the steering elements 56 ispulled (FIG. 27B), only the membrane 34 is deflected. The catheter 57remains unchanged or flexes just slightly. FIG. 27C shows a membrane 34with four steering elements 56 mounted on a steerable catheter 57. Inthis embodiment, when the steering element 56 is pulled, the membrane 34and the distal end of the catheter 57 can both flex. In an alternativeembodiment, only the membrane 34 can flex.

The catheter shaft can also include an anchoring system for stabilityand orientation. For example, suction can be applied through the shaftto stabilize the device over a specific region on the tissue. Thecatheter shaft can also be used to inflate the expandable membranestructure with a gas or fluid. This will be described in more detailbelow.

Assessment and Control of Energy Transmission to Tissue

Excessive energy applied to tissues can cause collateral damage such ascharring and clotting. Conversely, the lack of good apposition ofelectrodes to target tissues can result in sub-optimal transmission ofenergy particularly in anatomical areas having complex three-dimensionalgeometries. As such, assessing the progress of energy transmission aswell as adjusting and controlling the energy delivered can be used,particularly without the need for removing the device is beneficial. Thedevices described herein can include other features to assess andcontrol the energy transmission in real-time. For example, the devicesdescribed herein can include temperature sensors, mapping electrodes,irrigation mechanisms, visualization systems, radiopaque markers, fiberoptics, pressure sensors, heat dissipation pattern recognition software,impedance measurement software, anchoring mechanisms and other controlmechanisms as will be described in more detail below. With reference totemperature measurement, the electrode assembly 105 or the distal end ofthe catheter shaft may incorporate a microwave radiometer which canmonitor temperature remote form the sensor within a target tissue. Thisis in contrast to more traditional temperature sensors such asthermistor or thermocouples which require contact with the tissue ofwhich the temperature is being monitored. Such a sensor is especiallyuseful when the target tissue volume is within a tissue mass and not onthe surface to which the ablative elements are in contact. Such atechnology is described in US Patent Application Pub. No. 2009/0312754,which is incorporated by reference in its entirety.

Pressure sensors can be mounted within the electrode assembly 105 or inthe irrigation pump 1005. Such sensors will allow for control of thepressure internal to inflatable structure 34 of the electrode assembly105. The output of such devices can help the user to understand contactpressure. Additionally, such pressure information can be used to controlthe conformability of the expandable structure. In particular bymaintaining the internal pressure of the expandable structure a levelwhere tension in the walls of the structure are minimal when thestructure is not in contact with any tissue structure, the walls andaffixed electrode will be more conformable to the target tissuestructures on application by the user. Such pressure control will alsoenhance the swiveling action described with reference to the toroidalstructure of FIG. 18H.

Pressure sensors can also be used to monitor that electrode irrigationthrough irrigation holes 7 is maintained and properly functioning whenthe system is run under flow control. Holes can be sized and distributedsuch that within a given pressure range the flow rate of irrigationfluid is maintained within predetermined boundaries. Alternatively, twoflow sensors and a restrictor may be used as a flow monitor to verifyproper system performance. Irrigation flow ranges will depend on theparticular device and its intended use. Flow ranges of particular meritare in the range of 0.1 to 0.4 mL/min/mm̂2.

Cooling procedures, either by direct irrigation at or near theelectrodes or circulating cooling fluids through the expandablestructure, are especially useful when the target tissue is not at thesurface to which the electrodes are in closest proximity, but deeperinto the adjoining tissue. Cooling the expandable structure or theirrigation fluid can allow for higher energy delivery while protectingthe tissue near or in contact with the expandable structure while stillallowing damage to tissue further away from the electrode. One suchembodiment which allows for irrigation is shown in FIG. 63A. Themembrane 34 is attached to the outer shaft 57 at the proximal end and toinner shaft 134 at the distal end, the inner shaft 134 being of asmaller diameter than the shaft 157 allows for passage of saline 30 inbetween the two shafts. The ends of the membrane may be thickenedsections 35. In this particular embodiment, the flex circuit 89 isaffixed to the inner catheter 134 and the distal branches of the flexcircuit 87 are affixed to the membrane 34. Passage of saline 30 or otherirrigation fluid is allowed as the flex circuit is slotted in thetransition region. A close-up of the construction of FIG. 63A is shownin FIG. 63B. The distal branches of the flex circuit 87 are attached tothe outside of the membrane 34, so the transition from the attachment tothe inner shaft 134 to attachment to the outer shaft 57 occurs at ornear the membrane junction. This transition section will also containthe slotted features for saline passage. The membrane at this attachmentpoint is not attached to the inner shaft 134 which allows the spacenecessary for saline 30 to flow through into the membrane and provide acooling mechanism.

FIG. 63C shows an alternate embodiment which can be used both for theirrigation and for recirculation of a cooling fluid. This embodimentexpands on the previously described embodiment in FIGS. 63A and 63B, byincorporating an inner shaft 134 with two lumens, one of which is usedas a return for the cooling fluid. The membrane is inflated with saline30 via the inflation lumen 36 and, saline 30 exits via the opening intothe flow return lumen of the inner shaft 134. The other lumen in theinner shaft 134 is used as guide wire lumen 133. Inner shaft 134 and theguidewire lumen 133 may be separate entities of a multi-lumen catheter.Irrigation may also be incorporated with a circulating fluid coolingsystem by additional saline exit holes at the membrane as previouslydisclosed. Irrigation and recirculation cooling are facilitated by theirrigation pump 1005 and irrigation source 1003 depicted in FIG. 64. Insituations where only irrigation is provided these system components maybe replaced with a spring loaded syringe.

In combination with the cooling procedures just described theconfiguration of the power source and means of power application to theelectrodes and thereby the tissue can play a significant role inprotecting the tissue more proximal to the electrodes allowing thegeneration of ablative energy deeper into the tissue. With reference toRF ablation and cooling by irrigation or recirculation, the twogenerator (RFG) electrode configurations presented in FIG. 67A-67B areof particular interest. In FIG. 67B is presented a somewhat traditionalRFG arrangement. Two RFGs 48 are connected to two electrodes 6 and whenproperly energized current 2 travels between the electrodes. In thisconfiguration the negative outputs are connected in common across thebank of RFG's powering the electrodes. In such a configuration, pulsingRF will allow tissue closest to the cooling means to dissipate heatenergy without heating the cooling means. The heat generated deeper intothe tissue during the on time of the pulse is dissipated more slowly asthe thermal resistance between it and the cooling means is higherthereby minimizing substantial heating of the tissue surface proximal tothe electrodes. In FIG. 67A, an alternate arrangement of RFG electrodeinterfacing is presented. In this configuration each RFG 48 interfacesacross a pair of electrodes 6. Each RFG 48 and its paired electrodes 6are completely isolated from one another. Sets of paired electrode areenergized simultaneously. In such a configuration the current 2 in thearea between the electrodes 6 is doubled there by increasing the powerby a factor of 4. As illustrated only current at the surface of thetissue is portrayed, but in fact the effect is occurring in 3dimensions. Combinations of these techniques may be used to moreeffectively ablate tissues further from the electrodes while providingsome protection to the tissue in close proximity.

It should also be appreciated that a variety of elements are describedherein and that they can be used individually or in a variety ofcombinations. Features described herein in the context with or respectto one device, assembly or system can be implemented separately or inany suitable sub-combination with other devices, assembly or systems.

Sensing Electrodes

The devices described herein can include one or more electrodes that canbe used for a variety of functions, including but not limited toablation, sensing, stimulating and/or mapping. Mapping electrodes can beused, for example, to sense intrinsic cardiac activity and measure theconduction block during and/or after ablation for the treatment ofatrial fibrillation. In an embodiment in which atrial fibrillation isbeing treated, mapping electrodes can be incorporated to measure EKGduring the procedure without the need to introduce a separate device.The variety of electrodes can be deposited using the same or similartechniques and materials as described above.

In an embodiment, the electrode assembly includes a combination ofmapping and ablation electrodes. The mapping electrodes can beinterspersed between the ablation electrodes on the electrode assembly.For example, a small mapping electrode 51 can be positioned in themiddle of a larger ablation electrode 6. Each of the ablation 6 andmapping electrodes 51 can be connected to their own individual trace 16.The configuration of mapping electrodes 51 can allow for confirmation ofconduction block by comparing conductivity before and after ablation.Further, the proper number of these mapping electrodes 51 can helpidentify the direction of electrical signals to confirm properconduction block. In an embodiment, at least 10 small electrodes can bededicated for mapping. In another embodiment, at least 20 smallelectrodes can be dedicated for mapping. The mapping electrodes can beevenly spaced and arranged in a pattern similar to the ablationelectrodes. In addition, the larger ablation electrodes can also providemapping capabilities but the smaller mapping electrodes provide a moreaccurate measurement.

One or more mapping electrodes 51 can be incorporated with the flexcircuit 89. As shown in FIG. 7A-7E, mapping electrodes 51 can beconnected to the flex circuit 89 via a conductive pad 59. The mappingelectrode 51 can be located on top of or in between two electrodes 6,such as ablation electrodes, and remain electrically isolated from theelectrodes 6. Each of the ablation electrode 6 and the mapping electrode51 can have their individual conductive traces 16. The mapping electrode51 can be about the same size as its conductive pad 59 or can be laidover both the conductive pad 59 and the temperature sensor 90, if inproximity. The temperature sensor 90 and corresponding conductive traces16 can be insulated from the mapping electrode by a non-conductiveadhesive for example. As shown in FIG. 7E, the mapping electrode 51 canbe positioned more distally on the flex circuit such that lessadvancement of a catheter is needed for measurement of an electricalsignal when measuring inside the pulmonary vein.

In an embodiment, a mapping electrode 51 can be positioned on anexpandable membrane 34 having ablation electrodes 6. FIGS. 28A-28D showembodiments of an expandable, closed membrane structure engaged in thepulmonary vein 80. The membrane 34 can include multiple electrodes 6deposited thereon. Some electrodes 6 can be deposited on a region of themembrane that has a larger diameter. This region of the membrane 34 canbe more proximal and, for example, contact the antrum of the pulmonaryvein 80 to create an energy transmission line on the tissue 83. Thesmaller mapping electrodes 51 can be deposited near a distal region ofthe membrane 34 for mapping electrical activity originating from theveins. A guidewire 40 is shown and can be used for better positioning ofthe membrane 34. FIG. 28B shows an alternate embodiment in which theguidewire lumen is retracted proximally to decrease the size of themapping section of the membrane 34. This can allow for mapping insmaller anatomical regions.

In another embodiment, the mapping electrodes can be positioned on anexpandable membrane 34 having the mapping electrodes 51 between theablation electrodes 6. FIGS. 28C-28D illustrate an electrode assembly105 which is partially deflated prior to introduction into the pulmonaryvein 80. Once inside the pulmonary vein 80, the electrode assembly 105can be re-inflated if necessary to ensure good tissue contact of themapping electrodes 51. A guidewire 40 is shown and can be used forbetter positioning of the membrane 34. FIGS. 28E-28F illustrate anembodiment where ablation electrodes and mapping elements are helicallyarrayed around the cylindrical electrode structure of FIG. 18P. In thisembodiment the mapping electrodes are arranged in a helical patternbetween two sets to ablation electrodes.

In an embodiment, folding of the electrode assembly 105 and deflation ofthe expandable membrane 34 exposes the mapping electrodes 51 (see FIGS.24A-24B). The electrode assembly 105 can fold preferentially when theexpandable membrane 34 is deflated. The deflated assembly with exposedmapping electrodes 51 can be inserted into the pulmonary veins and usedto map the electrical signals. Once mapping is performed, the membrane34 of the electrode assembly 105 can be re-expanded or re-inflatedallowing for the ablation electrodes 6 to be used at their full size.During deflation, the membrane 34 can begin to fold at areas of themembrane 34 not covered by the flex circuit or areas adjacent to theflex circuits 89. The electrodes 6 can also fold in this process as theelectrodes 6 are flexible and carry similar mechanical properties as thebare membrane 34. FIG. 24A shows an expanded membrane 34 ready forablation. The flex circuits 89 are shown to contain one mappingelectrode 51 each, although there can be one or more mapping electrodes51 per flex circuit 89. FIG. 24B shows the membrane beginning to fold,initially at the sections not covered by a flex circuit such that theflex circuits 89 remain exposed. It is important to note that themembrane may not be fully deflated for this procedure. Also,re-inflation of the membrane once inside the pulmonary vein is possibleto ensure the mapping electrodes 51 are in full contact with the tissue.

The mapping electrodes 51 can also be positioned on a device separatefrom the ablation assembly such as a second expandable structure asshown in FIGS. 29A-29C. FIG. 29A shows an example of a two balloonintegrated ablation and mapping system having a separate balloon formapping 69. This second balloon 69 can have a separate inflation hole68. The guidewire lumen can be located on one side of the balloon 69 toallow for better control of the balloon 69 position. The second balloon69 can also be used to anchor the electrode assembly during use. FIGS.29B and 29C show a proximal ablation balloon 34 coupled to a distalmapping balloon 69. The two balloons can be part of a single catheter orcan be separate devices. Each of the balloons can include electrodes forablation and/or mapping, or electrodes to perform other functions suchas sensing or stimulating. A guidewire 40 can be used for example tocenter the mapping balloon 69 for better positioning of the mappingelectrodes 51.

In an embodiment, the mapping electrode structure can be a tubularstructure such as a mapping catheter 45 as shown in FIG. 30. Thecatheter 45 can serve as a guidewire for the ablation assembly as wellas provide mapping information. The distal end of the mapping catheter45 can wrap around an inside surface of the pulmonary vein 80 andmeasure electrical signals. FIGS. 31A-31B also show a linear mappingelectrode catheter 45. The mapping catheter 45 can be used also as aguidewire and can be the same diameter and length of a standardguidewire. In an embodiment, the mapping catheter 45 can be betweenabout 0.035″ and 0.038″. In an embodiment, the diameter of the mappingcatheter 45 does not exceed 0.035″ and can be interchanged with aconventional 0.035″ guidewire. The mapping catheter 45 can bemanufactured of a flexible outer shell with an inner diameter thatallows for a core element (not shown) to be inserted which willdetermine the shape, size, and stiffness of the catheter. As shown inFIG. 31A, the core can create a loop shape on the catheter 45 where themapping electrodes 51 can be located. The loop as shown in FIG. 31A canbe off-center or centered. The loop shape of the catheter 45 can beadjustable in size and can conform to the pulmonary vein for mapping. Asection distal to the electrodes 51 can be atraumatic and behave like astandard guidewire tip and terminate as a standard guidewire, forexample a J-tip as shown. The distal end can be closed such that it doesnot allow the core to protrude beyond the tip. A steerable element (notshown) can be included to manipulate the distal end of the catheter.

The mapping electrodes 51 can be deposited using the same or similartechniques and materials as the electrodes described above. Theelectrodes 51 can be formed with electro-conductive ink which can bepainted, printed, sprayed, deposited or otherwise transferred onto thecatheter as described above with respect to the ablation electrodes. Theink can include radiopaque additives for visualization under fluoroscopyor a radiopaque ink pattern can be included adjacent to or on top orbelow the electrodes. A thin, conductive film and/or conductive adhesivegel can be cut into strips and wrapped around the catheter to serve asthe mapping electrodes 51. Use of a conductive adhesive film or gel canalso serve to secure the end of the flex circuit. The conductiveadhesive can be created by mixing conductive particles, such as silverflakes, into a flexible adhesive.

During mapping, the catheter 45 can be extended distal to the expandedmembrane 34 as shown in FIG. 31A. If not in use, the shaped section ofthe mapping catheter 45 can be retracted into or proximal to theexpanded membrane 34 as shown in FIG. 31B. A mapping wire can be thesame diameter of a guidewire. In an embodiment, the proximal handle endof the mapping wire can be detachable to allow for other devices to beinserted over the mapping wire.

In another embodiment, the mapping electrode structure can include ascaffold or braided, self-expanding structure 98 that can be pusheddistal to an expanded membrane 34 and electrode assembly 105 as shown inFIG. 32A-32B. The mapping structure 98 can be covered by a membrane 54and can include one or more mapping electrodes 51. In its retractedconfiguration as shown in FIG. 32A, the mapping structure 98 can beelongated, narrow and positioned within the guidewire lumen. The mappingstructure 98 can be attached to a moving element 55. The lumen canremain open for a guidewire 40 to travel through. When mapping isperformed, the mapping structure 98 can be pushed distal to the expandedmembrane 34 and can self-expand (see FIG. 32B). The mapping structure 98can have a tapered or funnel-shaped structure near where it attaches tothe moving element 55. The funnel shape can allow for easier retractionof the mapping structure 98. Mapping electrodes 51 can be mounted on theexpanding portion of the mapping structure 98 in a variety of patterns,such as a single or multiple rows.

In another embodiment, the mapping electrode structure includes amapping wire (see FIGS. 33A-33B). A pre-shaped core 74 can be used witha coil 75 wound tightly around it. The flex circuit main lead 17 of theflex circuit 89 can be wrapped and bonded over the surface of the coil75. Multiple flex circuit main leads 17 can be used in the flex circuit89 and the conductive layer 96 can be located at specific intervals. Themapping electrodes 51 can be formed circumferentially around the wireusing conductive ink at each of the conductive sections 96 as describedabove. FIGS. 33C and 33D illustrate another embodiment of a mappingwire. In this embodiment, a pre-shaped core 74 can be used and a flexcircuit 89 wrapped over it. An insulated coil 75 of a non-conductivematerial can be wound around the inner assembly, tightly at the proximalend and varying at the distal end. The sections that are not tightlywound can correspond to the conductive sections 96 of the lead 17. Aconductive filler material 26, such as an adhesive, epoxy, or the like,can be used to fill the gaps between the flex circuit main lead 17 up tothe surface of the coil 75. The mapping electrodes 51 can be formedcircumferentially around the coil using conductive ink at each of theconductive sections 96.

FIGS. 34A-34F show various embodiments of a flex circuit 89 that can beused for the mapping wire. Conductive traces 16 on a flex circuit 89 canend in an L-shape. The proximal end of the lead 17 can be routed to thehandle (not shown). The short L-arm of the trace 16 can be exposed andprovide the conductive pad 59 for the electrodes. The flex circuit canbe wrapped over the inner assembly of the mapping wire so that theconductive section forms a loop around the core and connects to itselfas shown in FIG. 34B. The loops then can become the electrodes 51themselves or the electrodes 51 are formed using the same or similarconductive material as described above. FIGS. 34C and 34D show twoembodiments of the termination of the conductive section. In a firstembodiment, the tabs at the end can be bonded or secured in place viaadhesive or an outer bonding layer without disturbing the conductivepad. In another embodiment a self-locking mechanism can be used. FIG.34E shows straight traces 16 on a flex circuit 89 with conductive tips59 ending at different locations relative to the edge of the flexcircuit 89. The flex circuit 89 can be wrapped over the inner assemblyof the mapping wire with each conductive section ending at specificlocations on the length of the catheter. Alternatively, as shown in FIG.34F, the traces can be wound around the inner assembly similar to acoil. At each conductive section, electrodes 51 can be laidcircumferentially around the inner assembly.

The devices and electrode assemblies described herein can also includeone or more pairs of pacing and capture electrodes 91 to verify that thelesion created was effective in obtaining action potential block throughthe ablation line. As shown in FIG. 12, the large electrodes 6 can beused to create the ablation lesion lines for the treatment of atrialfibrillation, for example, as current 92 is passed between the adjacentelectrodes 6. Current 92 can also skip over one electrode to reach thenext to create the desired line as shown in FIG. 12. The pattern ofelectrodes 6 can be designed to create segments of interconnectinglines, for example to isolate the pulmonary veins and other areas in theheart. Multiple applications of energy can be applied by the electrodes6 to adjacent or overlapping tissue regions. Pacing and captureelectrodes 91 can be used, for example during creation of a lesion withthe RF power on or in between delivery of energy. In an embodiment, twoor more sets of pacing and capture electrodes 91 can be included. Oneset of electrodes 91 can deliver the pacing action potential and theother set of electrodes 91 can be located behind the lesion line to becreated to sense or “capture” the action potential delivered. When theablation line is complete and there are no open electrical gaps in thetissue, a single pair of these pacing and capture electrodes 91 (onepacing, one capturing) may be used to verify the action potential block.Whereas during creation of the first portion of the lesion line at thestart of ablation energy application the action potential can travelaround the lesion line to reach the capturing electrode. In thisscenario, a larger number of (e.g., more than two) pacing and captureelectrodes 91 can be used to identify the direction from which theaction potential came. The pacing and capture electrodes 91 can be usedto identify whether the action potential came through the lesion line oraround it thus identifying where additional energy transmission may benecessary. The multiple pacing and capture electrodes 91 can detectdirection of the action potential by identifying which electrodedetected the action potential first, second, third, fourth and so on.With this feature, the user can verify signal blockage after eachsegment of the lesion instead of waiting until the overall lesion iscreated.

Control of Energy Transmission

The electrode assemblies described herein are conformable such that theyprovide good contact with the target tissues, especially tissues havingcomplex three-dimensional geometries. Mechanisms can be incorporatedinto the devices described herein that improve contact of the electrodeassembly with the target tissues. In an embodiment a support structuresuch as a balloon can be used to press the electrode assembly againstthe target tissue (see FIG. 35). In this embodiment, a distal andrelatively small expandable electrode structure 34 that includeselectrodes 6 on its outer surface is positioned against the targettissue. A larger proximal support structure 39 can assist in positioningthe electrode structure 34 by pushing the smaller electrode structure 34against the tissue. A guidewire or guiding rod 85 is shown that can alsobe used to assist in positioning.

Heat and current can dissipate quickly away from a region to be treatedif for example a heat sink is present such as a near-by pool of bloodsuch as a large artery, vein, or the coronary sinus. This results insections of the tissue not getting sufficient energy transmission andthe failure of a conduction block. Because of the poor heat transfer ofenergy through gas compared to a liquid such as blood, a fluid-tightstructure filled with a blood-safe gas, such as carbon dioxide orhelium, can be provided near the location of energy delivery. As shownin FIGS. 36A-36B, a gas inflated balloon 94 can be placed in thecoronary sinus for example and used such that current 2 can pass fromthe electrodes 6 on the electrode structure 43 to a reference electrode6 on the gas-inflated balloon 94. The tissue between can then beappropriately ablated. The gas-filled structure can also be used fortemperature measurement and feedback.

As described above, the flex circuit 89 can have temperature sensors 90mounted on conductive traces 16 near, on or between electrodes 6 incontact with the tissues. The temperature sensors 90 provide feed backto the user as to the temperature of the target and surrounding tissuessuch that the device and/or the user can modulate energy supply andcharring or excessive coagulation can be avoided. Controlling thetemperature, for example using irrigation at or near the tissuetreatment site, is another way in which charring can be prevented. Asshown in FIGS. 37A-37C, irrigation holes 7 can be positioned near one ormore of the electrodes 6 to deliver a cooling fluid to the region andmaintain consistent, predictable pattern of energy transmission. Thefluid can include a non-conductive or conductive irrigation medium. Thefigures show irrigation holes 7 for three electrodes 6, but it should beappreciated that more or less than three electrodes 6 can haveirrigation holes. In an embodiment, all electrodes 6 have one or moreirrigation holes 7. The irrigation holes 7 can be contacting or adjacentto an electrode, for example surrounding the border of the electrode 6.In another embodiment such as shown in FIG. 37B, the irrigation holes 7can be placed directly on the surface of the electrode 6 near the edgeof the electrode 6. It should be appreciated that the irrigation holemay be placed anywhere on the electrode 6. FIG. 37C shows yet anotherembodiment with irrigation holes 7 located in between two electrodes 6so adjacent electrodes 6 share a set of irrigation holes 7. It should beappreciated that the configuration of irrigation holes 7 to electrodes 6can vary and that the configurations provided in the figures are forexample only. FIG. 37D shows a single irrigation hole 7 located at thecenter of each electrode (only six holes are shown). In one embodiment,these irrigation holes 7 can match with holes placed on the flex circuitconductive pad 59 (see FIG. 3B). In one embodiment the flow rate of theirrigation fluid can vary and be controlled to a desired level. Theirrigation flow rate can be set to a minimum level to maintain pressurewithin a closed membrane, such as a balloon for example, whilepositioning or orienting the catheter. Alternatively, cooling fluid canbe circulated within a closed membrane without the use of irrigationholes.

When irrigation fluid delivery is the means by which the ballooninflation is maintained, the size and number of holes becomes important.The fluid resistance of the sum of the holes should be such that for therequired flow of irrigation fluid the pressure drop across the sum ofthe holes is that required to maintain the balloon inflation. As thepressure drop across a hole for a given flow rate varies as a 4th orderfunction of the diameter, a preferred embodiment has many smaller holessuch that more averaging can occur. In addition to averaging, when lowerexit fluid velocities are desired, many smaller holes provides anadvantage over fewer larger holes.

In FIGS. 37E-37F are illustrated irrigation holes 7 incorporated as partof the flex circuit 89. When the irrigation hole 7 is configured in thisfashion the increased stiffness associated with the flex circuitsubstrate 52 singly or in combination with the conductive layer 96 andother layers may be used to advantage as a means to provide extrastrength to the irrigation hole and thereby prevent tearing of themembrane 34 at the irrigation hole during manufacture or use. The flexcircuit in proximity to the hole can be affixed to the expanded membrane34 via an adhesive 95 or other bonding process during manufacture. Thehole 7 in flex circuit 89 can additionally be used as a template forhole placement by drilling, puncture, or other suitable process duringmanufacture. In this fashion placement relative to the electrodes andthe size of hole may be more closely controlled, which are both factorsimportant in the process of irrigation. Both hole placement relative tothe electrode and the cross section and cross sectional area of the hole7 will be important in controlling the volume flow of irrigation fluidin proximity to the electrode 6. The irrigation hole as illustrated inFIGS. 37E-37F has been shown such that the irrigation hole passesthrough all the electrode 96, substrate 52, and adhesive 95, layers ofthe electrode assembly structure 105 of FIG. 1A. The irrigation hole 7as described may, however, be used in any electrode structure 105 hereindescribed incorporating a flex circuit 89. The irrigation hole 7 mayalso be configured such that it passes through any or none of the layersassociated with the disclosed structures of electrode structure 105 solong as the irrigation hole 7 passes at least one of the layersassociated with the flex circuit 89.

The devices and electrode assemblies described herein can incorporate avariety of mechanisms that allow the user to assess the extent,orientation and quality of treatment line as well as the orientation ofthe electrode assembly itself in real-time during a procedure withoutthe need to remove the device. For example, energy transmission can bevisualized and assessed through the deployable membrane of the devicesuch as, for example, using incorporated fiber optics or a camera on achip. FIGS. 38A-38G show a balloon 34 having electrodes 6 mounted on itssurface as well as a fiber optic scope 38 to visualize the tissue as itis being ablated. The scope 38 can be positioned on an interior of theexpandable structure 34 as shown in the figures or an exterior surfaceof the expandable structure 34.

In an embodiment, more than one fiber optic scope 38 can be used in theelectrode assembly 105 (see FIGS. 38D-38G). The fiber optic scopes 38can be wrapped helically around an inner shaft 12 with a flexible shaft57 or be placed adjacent to the inner shaft 12 to achieve a desiredfield of view (“FOV”). The scope(s) 38 can also be fitted with angularviewing optics to achieve a different view. For example, FIG. 38Dillustrates the scope 38 wrapped around the inner shaft 12 to achievethe FOV shown. The same scope 38 in FIG. 38E goes straight through theshaft 12 but to achieve the same FOV, an angular viewing optic can beused. In one embodiment, the fiber optics scope 38 can be movable alongthe axial length within the membrane 34. This can aid in theconfirmation of good apposition to the tissue when the electrodeassembly 105 is already in place. FIG. 38G shows a close-up view of fourscopes 38 wrapped helically around an inner shaft. Radiopaque markerscan also be used to aid in determining the orientation of the electrodeapparatus during use. FIG. 20A shows radiopaque visual orientationmarkers 49 coupled to the support arms 44. The orientation markers 49can have a variety of specific shapes that can be used, for example by asoftware projection algorithm from the fluoroscope output. Mapping datacan be combined with orientation data from the markers 49 to visualizeand allow the user to select which electrodes 6 to activate and use forthe desired energy transmission. A user interface can display theorientation of the device, for example on a screen on the RF generator,and this image can also be superimposed on a fluoroscopic view. FIG. 38Hillustrates a front view of an electrode assembly 105 incorporatingvisualization system and the field of view for one of four such opticalsub-assemblies incorporated in the optical assembly. Each of the opticalsub assemblies incorporates an optics structure 142, which interfaces toan illumination fiber 141, a 200 micron fiber bundle 140, such as theSumitomo Image Guide IGN-02/03, and an optics structure 142. A quartersection of the electrode assembly 105, with flex circuit 89 (not shown)and inner shaft 57 for visualization of the fibers, is depicted in FIG.38I. Illumination fiber 141 and image guide 140, in the depictedembodiment, travel within inflation lumen 36 (see FIG. 6C) to handle1006 (not shown) and on to visualization system control 1004 (notshown). The sub-assemblies are fitted into the toroidal expandablemembrane 34 singly and locked in place around the inner shaft 57 at thetime of assembly of the visualization system. Other arrangements notdepicted route the fiber bundle and illumination fiber through anadditional lumen in the inner shaft 134 (not shown).

In any of the embodiments represented in FIGS. 38 A through I, thevisualization systems incorporating fiber scopes and fiber opticillumination may be replaced with visualization systems whichincorporate either cameras and/or LEDs at the distal end of the ablationsystem. FIG. 38J depicts a component sub assembly of such avisualization system comprised of two sub assemblies. The two subassemblies comprising sub assembly 210 are a camera sub assembly and anillumination sub assemble, each fabricated by molding the activecomponents into an optical grade of polymer. The visualization system ofFIG. 38J is configured similarly to the structure described in FIG. 38I,however the optical fibers which comprised the fiber optics scope orimaging bundle 140 has been replaced with camera 240, and theillumination fiber 141 has been replaced with LED 241. The camera ismounted in optic structure 242 and the LED is mounted in optic structure243. As depicted the three visualization sub assemblies comprise a totalvisualization system 200. The three sub assemblies comprising the totalsystem provide for a smaller fabrication cross section and ensuingadvantages as described elsewhere here in. Such a complete system isdepicted in FIG. 38K mounted within a toroidal flexible membrane 34structure for carrying ablation electrodes as described herein. Avisualization system alternatively may incorporate more or lesssubassemblies 210. A flex circuit as described herein can be adapted tointerface a camera when used.

The visualization system of FIGS. 38 J, K, and L are structured suchthat the FOV for both the camera element and the illumination elementare fixed relative to the directions in which they point, which asdepicted are at an angle of about 60 degrees relative to the cylindricalor longitudinal axis of inner shaft 134. Camera elements 240 and LEDelements 241 are distributed about 120 degrees apart from adjacentcamera elements and LEDs, respectively, around the longitudinal axis.The camera elements and LEDs are offset with respect to each other byabout 60 degrees. In this fashion the FOV's for the camera elements andthose for the LED elements overlap as depicted in FIG. 38L. Suchembodiments have an added advantage in that during delivery they canflex in towards the center of the opposite of what is shown and therebypresent a reduced cross sectional profile. Where such a feature isdesirable, the camera might be placed proximal to the LED.

Another alternative visualization system in which the direction in whichthe FOV's for the camera and illumination elements may be adjusted isdepicted in FIGS. 38M-38Q. In this embodiment the optics structures 242,along with associated camera and LED, are mounted on flex circuitbranches 87 of a flex circuit 89, as depicted in FIG. 38M, where onlyone optics structure 242 is shown mounted to one of the three branchesfor clarity. As the two ends of the flex circuit 89 are displacedaxially relative to one another, the branches 87 flex, thereby adjustingthe direction relative to the cylindrical axis of the shaft (not shown)to which the visualization system is pointed. In an embodiment such asthat of FIG. 62, the distal end of the visualization system is attachedto an inner shaft and the proximal end to an outer shaft or theassociated hubs of the toroidal balloon. The distal end of thevisualization system of FIGS. 38M and O is that closest to the camera.The flexing branches 87 of the flex circuit 89 may be modified tofacilitate preferential bending at bend points 245. The substrate may benarrowed at these points such that the width is reduced and or thesubstrate and or electrical traces may be thinned at these points.Alternatively a NiTi element may be incorporated in the flex circuit atthese points.

In one embodiment of the optics structure 242, the structure is cast inan optical grade of polymer. In such an embodiment some or all of theoptics associated with camera and illumination source may be features ofthe optics structure. Such features known to those skilled in the artare not shown here. The optics structure 242 may additionallyincorporate features which allow for better mechanical interfacing withflex circuit branch 87. The optics structure may also incorporateoptical dams to isolate the source light from entering the camera fromwithin the optics structure. Alternate preferred embodiments may befabricated by injection molding as used for fabricating optics.

In the embodiments depicted in FIG. 38 the fluid used to inflate theflexible membrane 34 and the flexible membrane itself will betransparent to the illumination and camera optical pass bands. Anexemplary inflation fluid is saline with or without a radiopaquecontrast media. A few of the many possible materials appropriate for theflexible membrane are PET and Polyurethanes. In some alternatives CO2may be used to inflate the membrane. This is particularly advantageouswhen a camera capable of imaging in the IR is used. Such a system wouldhave particular advantage in monitoring electrode and/or tissuetemperature during an ablation procedure.

FIGS. 38 N and O illustrate the visualization system of FIG. 38M andassociated FOV's for the sub assemblies 210 in two different states offlexure. In FIG. 38N, the flex elements are flexed at about 60 degreesrelative to the shaft longitudinal axis and in FIG. 38O they are notflexed and the FOV's are pointing in a direction substantially normal tothe shaft's longitudinal axis. As can be seen in FIGS. 38N and O thereare FOV overlap regions 252 associated with some range of angles off ofthe shaft axis and there are some range of angles for which there is nooverlap. When working with multiple cameras, these overlap regions haveparticular value. At a minimum, in regions where such overlaps exist, acontiguous image of the target tissue is available. Additionally thefeatures within the overlap regions may be used as a basis to processthe individual images and knit them together into one contiguous imagefor presentation to the operator. In addition elliptical and cylindricallenses can be used to enhance overlap of FOVs. Image processingprotocols may also be used to remove distortions associated with suchlens use and variations in camera angle.

The adjustable visualization system of FIGS. 38M-38Q has additionaladvantage when camera optics are required to be simple such as for costrelated or camera volume related concerns. In such situations a camerawith a small FOV may be manipulated to view image particular featuresand/or multiple images which can be knit together to create an imagewhich covers a larger area.

When capturing multiple images from multiple cameras either sequentiallyor in parallel, or when capturing multiple images from a single camerasequentially, or both, areas within the images that have sharp featuresand are imaged in multiple FOV have particular value. FIG. 38Pillustrates the visualization system of FIG. 38M mounted in a fashionsimilar to that depicted in FIG. 38I where the toroidal ballooncomprises three electrodes 6. The illustration characterizes cameraswhich are facing five degrees off of the shaft angle. The electrodes aremarked to facilitate identification of specific locations within theFOVs. As illustrated they are numbered 1 through 3 and the numbers havebeen placed both on and off the electrodes. Marking features other thannumbers could also be used such as varying the shape of the electrode.Alternatively, any of the means described for the use of radio opaquemarkers could be used, for instance those illustrated in FIG. 40B. Inthe illustration of FIG. 38P the cameras will image the region betweenthe two circles 258 which represent the surface of the toroidal balloonwhich is in contact with a tissue surface. The full extent of the FOV's250 for the three cameras is shown, but it should be understood that theportions of the FOVs outside the image region will not image tissue. Inthe illustration of FIG. 38P the three cameras image the area 253 whereall three FOVs intersect. Pairs of cameras FOVs intersect in areas 252and areas 251 are imaged by only one camera. In this example themultiple overlap regions and the locational features greatly facilitatethe image processing required to knit the images into a contiguouswhole. The illustration of FIG. 38Q characterizes cameras with a tilt ofabout 45 degrees. In both figures the FOV for the cameras is about 120degree.

In alternate embodiments the visualization systems described herein canbe comprised of expandable structures with configurations other thantoroidal. FIG. 38R illustrates the visualization system of FIG. 38M witha cylindrical balloon structure. The distal direction is to left on thepage, and the remainder of the system has been left out for clarity. Asillustrated, the camera has a FOV of substantially 120 degrees and ispointed at substantially 15 degrees off the shaft axis. In such aconfiguration a contiguous image of the surface to which the balloonstructure is adjacent will be recorded by the tree cameras. The heightof the contiguous image will be the maximum length of the FOV overlapregion 252. In this configuration when the cameras are pointed at lessthan about 10 degrees the captured image will not be contiguous. In yetanother embodiment the fixed visualization system of FIG. 38J may beused. The design of the visualization system can be adjusted toaccommodate the constraints of the particular intended use. More camerascan be used when the constraints require fixed cameras and/or cameraswith smaller FOV. Alternatively, larger FOV and/or steerable cameras canbe used when constraints require less volume or cost amongst otherconsiderations. In yet another embodiment a single fixed or steerablecamera can be used and rotated thereby capturing multiple sequentialimages which can, by image processing procedures, be knit into acontiguous image.

Two additional exemplary features of the embodiments of thevisualization systems presented herein are the delivery profile of thecompleted visualization system and fabrication profile of thevisualization system or its components. The delivery profile is theprofile of the visualization system which is normal to the shaft axis inthe delivery configuration. The fabrication profile is the profile ofthe smallest component which can be assembled within the expandablemember. The fixed visualization systems described herein are comprisedof multiple sub-elements 242 and 243 which when assembled comprise thecompleted distal portion of the visualization system 200. FIG. 38K isexemplary of such a design using three sub-assemblies 210 to comprisethe whole assemble 200 that has a fabrication profile equivalent to thefront face subassemblies 242 and 243. The fabrication profile for thesteerable visualization assembly distal section described herein isapproximately the front facing surface of the optical structure 242 forthe configuration where each of the branches 87 are separate at thebeginning of fabrication and can thereby be introduced into theexpandable structure separately. In preferred embodiments the opticalstructure will be designed such that these profiles are minimized.Following introduction the distal ends are then fixed together. Thedelivery configuration for the steerable visualization system can insome embodiments be made smaller by allowing the individual branches tocompress into the center of the delivery lumen. In some embodiments thedelivery profile is smaller than the outer shaft.

In yet other embodiments the distal end of the visualization system ofFIG. 38M can be left free floating such that on delivery the device canbe compressed but on deployment it can spring into a deliveryconfiguration.

Thermochromic inks can be used to create locational markings as isindicated by the ring in FIG. 38P electrode number 3. Alternatively theentire back surface of the electrode could be covered with athermochromic ink, in which case temperature uniformity of the electrodecan be evaluated. Electrode 2 in the figure is represented as a group ofparallel lines of conductor separated by spaces and ringed by a commonconductor. Such an electrode facilitates viewing the tissue behind theelectrode during the ablation process.

FIGS. 3B, 39A-39E, and 40A-40B show various embodiments of radiopaquepatterns that can be used with an expandable membrane structure 34 forthe visualization and orientation of the placement of the electrodes 6onto the tissue as well as the overall shape of the expandable membranestructure 34. In an embodiment, the radiopaque markers 58 can be thinlines or “spines” along the longitudinal axis either between theelectrodes 6 as shown in FIG. 39A or directly across the center of theelectrodes as shown in FIG. 39B or 39C. These spines of radiopaquemarkers 58 provide an indication of distance between electrodes 6 andoverall shape of the balloon 34 against the tissue. In anotherembodiment, radiopaque markers 58 can be incorporated into the flexcircuits that are used to connect each electrode 6. Layers of denser,radiopaque material such as gold can be added to the conductive pads ofthe flex circuit 89 for visualization. The denser material can also beplaced at the distal branch of the flex circuit to create the thinspines. In this embodiment a thin layer of additional material can beused such that the surface or thickness of the electrodes is not alteredand an overall low profile of the device maintained.

In another embodiment the radiopaque markers 58 can form lines angledacross the electrodes 6 giving the user a sense of whether the electrode6 is, for example on the anterior or posterior side (see FIG. 39B). Inanother embodiment, the radiopaque markers 58 can be in the shape of an“X” across the electrode 6 allowing for the center and edges of theelectrodes 6 to be pinpointed (see FIG. 39C). An outline of theelectrode 6 can also be traced with radiopaque materials. In otherembodiments, the radiopaque markers 58 can include dots around ordirectly on top of the edges of the electrodes 6 such that they outlinethe shape of each electrode (see FIGS. 39D and 39E), or they may becentered within the electrode (not shown) as dots or other shapes.Alternatively an electrode material which is both radiopaque andconductive may be used to facilitate these embodiments. In such casesthe thickness of the electrode may be varied to adjust the radiopacity.In such an embodiment where it is desired to enhance the radiopacity ofthe center of the electrode, the full electrode is masked then printedthen re-masked to define the thickened area and printed again. This oralternate electrode fabricating techniques can be used in any of thecases where the patterns previously described are applied to theelectrodes. Other configurations, shapes, sizes of the radiopaquemarkers are possible.

The radiopaque markers can be placed on an electrode assembly atcircumferentially asymmetrical intervals along the membrane 34. If thedeployable membrane of the electrode assembly has an expandablestructure such as a balloon, the radiopaque markers can be placed atadjacent quadrants of the balloon or between specified electrodes thatare not evenly spaced apart. The markers can be the same or have varyingshapes and sizes. Alternatively, the markers can create a distinguishingpattern over the surface of the membrane. In an example, a firstquadrant marker can be one dot, a second quadrant marker can have twodots, and a third quadrant marker can have three dots and so on. Themarkers can include matching markers mounted on the shaft at the samespacing.

As shown in FIGS. 40A-40C, a radiopaque marker system can beincorporated on the membrane 34 of an electrode assembly. In anembodiment, two dissimilar markers 58 can be placed at just over 90degrees apart (quadrants 1 and 2) and three electrode widths apart.Matching markers 58 to those on the membrane 34 can be located on thedistal end of the shaft 57. Under fluoroscopy, the user can determinethe orientation of the electrode structure 105 based on the location ofthe markers 58. The use of dissimilar markers 58 as shown, or varyingnumbers of dots on each consecutive quadrant as described above, allowsa user to determine the orientation of the membrane 34 and determine thetarget energy transmission location. Such patterns may in addition befacilitated by using the techniques described with reference to FIGS.39D and 39E, where the patterns are created on the electrodes and notall electrodes receive the same treatment. Where rotational orientationis sought, radiopaque markers may alternatively be added to structuresother than those located on the membrane 34. Such an embodiment isillustrated in FIGS. 40D-40E. FIG. 40D illustrates a radiopaque ring 58affixed on the OD of shaft 57. FIG. 40E illustrates the ring in anunwrapped configuration where the one of a number of possible setfeatures are more easily seen. The transparent portion of the projectionpassing across the longitudinal axis of the ring created by the triangleand square cut outs has an image which continuously and uniquely variesthrough 360 degrees of rotation. The ring can be configured to belocated in alternate locations such as on the ID of outer shaft 57 orother cylindrical structures within, or on the of thickened membranesection 35 of membrane 34, amongst others.

FIG. 3B illustrates the integration of a radiopaque marker system 58directly onto the flex circuit 89. A set of markers 58 is shown on twoseparate branches 87 of the flex circuit 89, for example 1 line and 2dots. In the embodiment of FIG. 3D a number of the flex arms of the flexcircuit can be modified to enhance the radiopacity by incorporating aunique layer of appropriately radiopaque material, or modifying aconductive layer material, or conductive layer thickness, or both. Insuch an embodiment the arm incorporating electrode pad 59 c, and theforth, and seventh arms, counting from left to right, incorporate aradiopaque layer which extends from the proximal tab 116 to the distaltab 116 for the first arm, ⅔ that distance for fourth arm and ⅓ thatdistance for seventh arm. Such a unique layer may additionally becreated by adhering a foil of a radiopaque material such as silver,tungsten, tantalum, platinum, or gold to the branches of the completedflex circuit or be adhered to the flexible membrane 34 independent ofthe flexible circuit.

The spacing, number, shape and size of the markers 58 can play animportant role in defining the geometry and orientation of the device aswell as ease of use of the marker. The branches 87 of the flex circuit89 can be located at unique latitudes on the membrane 34, in particularan embodiment of a membrane 34 similar to those of FIGS. 18A-18M. Themarker system 58 can then lie at unique positions on the membrane 34. Ifthe markers are spaced out in adjacent quadrants, for example, and areof different shape and/or number, the user can readily recognize aparticular marker as quadrant I. Additionally, the temperature sensors90 and electrodes themselves can serve as radiopaque markers whichprovide an indication of overall shape of the expandable membrane 34. Insome embodiments thermistors of different sizes may be used anddistributed in such a way that sections of the electrode assemblybetween the thermistors are identifiable.

Other mechanisms can be included in the devices or electrode assembliesdescribed herein that allow a user to assess orientation and quality ofenergy transmission without the removal or repositioning of the device.For example, sensors located at or near the electrodes can beincorporated to detect tissue contact with the electrodes or the amountof pressure exerted on the tissue during a procedure. Because the amountof contact and pressure can have a dramatic influence on the depth andquality of the lesion being created, it can be important to assess inreal-time the extent of contact made with the tissue and the degree ofpressure being exerted. The depth of energy penetration and the abilityto detect tissue contact with the electrodes during transmission allowsa user to avoid thrombus formation and inadvertent charring of thetissue.

Tissue contact can be measured using a variety of techniques. In anembodiment, software can be programmed such that no significant hardwareneed be implemented. For example, the measurement of electrocardiogramsthrough the electrodes on the membrane. Signals obtained by theelectrocardiogram allow a user to determine whether the electrode is incontact or not. Algorithms can be employed to determine partial contactas well.

Another method to determine tissue contact with the electrode is toincorporate heat dissipation pattern recognition into the software. Ashort burst of RF heating can be applied to the electrodes and based onthe behavior of heat dissipation the software can recognize whether theelectrode is in contact with tissue or is in contact with only blood,for example. A faster dissipation of the heat applied would indicatecontact with flowing blood instead of tissue, which would retain theheat longer.

Yet another method to detect tissue contact with the electrode isthrough impedance measurements. Contact with tissue can show a change inimpedance as compared to blood. The amount of contact force may also beassessed through impedance measurements. This allows for properdetermination of not only electrode-tissue contact but amount of forcein which they are in contact, which could more accurately predict thedepth of the energy transmission to be performed. A number of variables(frequency and amplitude) can be adjusted to achieve the desirablethreshold and accuracy to determine the difference between tissue andflowing blood.

FIGS. 41A-41B illustrate another sensing mechanism using impedancemeasurements. The flex circuit 89 can contain two conductive traces 16having non-insulated conductive pads 59 near their distal end andlocated near or adjacent to the electrodes (not shown), which are inproximity to one another. Impedance can be measured between the twoconductive pads 59. In an example, when both conductive pads 59 are incontact with tissue, the impedance measurement will be generally high.When only one conductive pad 59 is in contact with tissue or both endsare not in contact, the impedance measurement will be generally lower.FIG. 41B shows a similar method that allows for larger conductive pads59. This may allow for partial tissue detection based on a larger rangeof impedance measurements.

Pressure sensors are known in the art and can be incorporated into theflex circuit. An example is a piezoresistive pressure sensor which canbe covered with gel, silicon or another material. Examples of thesesensors include GE NPD-240, GE NovaSensor P1602 and SiliconMicrostructures SM5102, EPCOS ASB1200V and T5300, and Intersema MS7212.The sensor can be placed on the flex circuits near or at the electrodes.

Micro-switches can be located at each electrode, for example withadditional hardware and/or software integration. FIGS. 41C and 41 Dillustrate an example of an electrode 6 broken down into 3 separateconductive patches 6 a, 6 b, and 6 c. Each conductive patch 6 a, 6 b,and 6 c can have a corresponding micro-switch that is physicallyactivated when tissue is in contact with the electrode. The switch andconductive patch are connected when in contact with the tissue. Once allthree patches 6 a, 6 b, and 6 c are connected the electrode 6 can beactivated. The flex circuit 89 can be arranged differently between thetwo figures which may define the overall flexibility and foldability ofthe assembly.

In another embodiment shown in FIG. 42, an electrode catheter 71 canincorporate radiopaque, longitudinal “arms” 60 that protrude out whenthe appropriate amount of pressure is being applied by the electrodecatheter 71 against the tissue 83. If there is no pressure exertedagainst the tissue 83 or not enough pressure being exerted, theelectrode catheter 71 has a slender profile with no protrusion of thearms. If too much pressure is being exerted, the arms 60 splay such thatthey can point backward. A specific shape of the arms can be anindicator of proper contact pressure. FIG. 43 shows an electrodecatheter 71 that includes an expandable element 62 such as a balloonthat can be controlled by a valve 61 or other fluid-control mechanism.When the appropriate amount of pressure is being exerted by theelectrode catheter 71 on the tissue 83, the valve 61 allows theexpandable element 62 to be inflated via an inflation lumen 36.Electrodes (not shown) can be placed on the distal tip of the electrodecatheter 71 for activation when the expandable element 62 reaches theproper size. The expandable element 62 can be inflated with a radiopaquedye or radiopaque dye can be injected into the bloodstream forvisualization.

Electrode Assembly Anchors

The devices described herein can incorporate various structural elementsthat provide further assistance in the manipulation and repositioning ofthe electrode assembly without the need for removing the device andreorienting the device. For example, the electrode apparatus can beindependently translatable over an anchor catheter or guide element thatis fixed in place at or near the target tissue. The anchor can provide astable reference point and act as an efficient, quick and controlledrepositioning device that the electrode assembly can slidably orrotatably move over, for example to contact the ablation pattern regionjust created. This allows a user to perform additional energytransmissions, for example in areas that did not result in fulltrans-mural ablation. Or a user can map and verify the effectiveness ofthe therapy, for example in areas of the tissue that are thicker orrequire a higher dosage of energy or several passes of energytransmission.

The configuration of the anchor device can vary including, but notlimited to, a suction catheter, an expandable member such as a balloonor basket, or suction pods that incorporate electrodes and suctionmechanisms simultaneously. In an embodiment where cells outside thepulmonary vein are to be treated, for example in atrial fibrillation, anexpandable element can be inserted within the pulmonary vein.

FIGS. 44A-44F show an embodiment of a membrane 34 that includes ananchoring basket 50. The membrane 34 is shown as having a balloonstructure, but the membrane 34 can have another shape and configurationas described above such as a single catheter that extends to ananchoring basket 50. FIG. 44A shows a guide 47 (catheter or wire) thatcan be anchored at the distal end by deploying the anchoring basket 50.The guide 47 can be deployed along the desired line 81. Once the guide47 is in place and optionally a visualization balloon and scope assembly(not shown) advanced over the guide to confirm correct placement andtissue contact, the membrane 34 can be retracted (or advanced) whileactivating electrodes to achieve the desired linear lesion 81 (FIG.44B). After the first linear lesion is made 81, the guide 47 can berotated around the anchor 50 and re-oriented to create a secondarylesion (FIGS. 44C-44D). Alternatively, a fully or partiallycircumferential lesion 81 can be created around the antrum of thepulmonary vein or in combination with the linear lesions described above(FIG. 44E). This can be done by maintaining the membrane 34 positionrelative to the guide 47, and rotating the membrane 34 around the axisof the anchor. Once the desired lesion set is completed, conduction canbe tested for example by monitoring electrical potentials via mappingelectrodes 51 located on anchor 50 deployed within the pulmonary vein(FIG. 44F) as discussed above.

As shown in FIGS. 45A and 45B, the anchor can also have an expandablestructure such as a balloon. The anchor 42 can have a variety of shapes.In this embodiment, the anchor 42 can be deployed, for example in thepulmonary vein 80 for anchoring and positioning of an element 43. Aguidewire 40 can be introduced in the pulmonary vein 80 to assist in thelocation of the anchor 42. The electrode element 43 is shown havingelectrodes 6 on its outer surface and a fiber optic scope 38 that can berotated for visualization around the circumference of the electrodeelement 43.

Controlled repositioning mechanisms using suction can also be used suchthat some portion of the anchor is in contact with the tissue whileanother portion is being repositioned. In an embodiment, suction tipcatheters can be used to anchor the electrode assembly. The suction tipcan be deployed within the pulmonary vein. A suction tip 1 can also beused for controlled repositioning of the electrode element. For example,one or more suction regions can be alternately turned on or off to allowa user to guide and move the device, such as an electrode catheter asshown in FIGS. 48A-48B, 49A-49D, 50, 51A-51C, and 52A-52D. Suction canbe incorporated with an optional inflatable element to improve energytransmission achieved in addition to anchoring such as shown in FIGS.44A-44F, 47, 53A-53E, 54A-54D and 55A-55C.

An anchoring catheter 15 can have a suction tip 18 to anchor on themyocardium wall of the pulmonary vein 80 to be used in conjunction witha separate electrode sheath 76 (see FIG. 14A-14B). Alternatively, anelectrode sheath 76 can be a single catheter that extends to ananchoring basket distal end 50 or terminates in a suction tip 18. FIGS.46A-46B and 47, show close-up views of the electrode element having anaspiration lumen 4 and a distal region that has an elliptical, roundedor funnel-shaped suctioning tip 1. The suction tip 1 allows theelectrode element to locate and anchor onto an area of the myocardium 83as well as transmit energy in the same region using electrodes 6. Thetissue 83 can be pulled inside the suction tip 1 for anchoring andenergy transmission. As shown in FIG. 46A, the electrodes 6 can be usedin a bipolar configuration allowing the current 2 to move from one sideof the suction tip 1 to the other. Current 2 can pass through the tissue83 in a pattern similar to lines 2. Alternatively, the electrodes 6 ofthe electrode element can be used in a monopolar RF energy delivery. Theelectrodes 6 can be on the inside surface of the suction tip 1 tocontact the tissue 83 directly or through a fluid layer such as saline.Irrigation holes 7 and irrigation lumens 8 can be included to reduce thechance of clotting and charring at the electrode site as well as preventexcessive heat build-up. The irrigation holes 7 can be placed on theinside and or outside of the suction tip 1. As shown in FIG. 47, thecatheter 71 can be a catheter having a flexible and torque-able shaftthat can be laser cut in a puzzle like pattern 3 out of metal or hardpolymer. The main flex circuit lead 17 can connect the electrode 6 tothe proximal end.

FIG. 48A shows a steerable sheath 9 and a two arm catheter 63 extendingfrom the distal end of the sheath 9. The two arm catheter 63 can includetwo suction tips 1 each of which can have electrodes to allow RF energytransmission between the two suction tips 1 of the catheter 63. The twosuction tips 1 can have a funnel shape each disposed with an electrode6. The suction tips 1 allow the electrode to be anchored independently.One suction tip 1 of the catheter can anchor onto the tissue, forexample by activating the suction, and the other suction tip 1 arm movedto the next target tissue region. Movement can occur by moving thesuction tip 1 guided for example by the pre-determined spacing betweenthe tips 1 and a tension wire 20 that can be controlled by the user (seeFIG. 48B). The tension wire 20 can be pulled to bring the two tips 1towards one another. Release or relaxation of the tension wire 20 canallow for the two suction tips 1 to spread apart such as due to a springforce in the material of the tips 1 and/or catheter 63.

Once the catheter 63 is positioned ablation can be initiated. Thesuction tips 1 can include one or more electrodes and one or moretemperature sensors. The two suction tips 1 can be spread apart andsuction turned on through both tips 1 before energy is applied.Alternatively, the suction can be turned on for a first tip 1 and thenturned on for the second tip 1 before energy is applied. To continue theenergy pattern one of the suction tips is turned off and is positionedin another location, for example by rotation or changing the distancebetween the tips using the tension wire 20. To achieve the desiredposition, the user can alternately turn on and off either of the tips 1and orient the catheter 63 as desired. When creating a particularpattern, the use can keep suction active on one of the suction tips 1and inactive on the tip or tips being moved. The main body of the sheath9 or the catheter 63 can have great flexibility and torque-ability. Thesheath 9 or the catheter 63 can include a laser cut pattern 3 or have abraided shaft that allows for the catheter to maintain one-to-one torquecontrol, such as after taking out the slack, while providingflexibility/bendability and enhance the ease of positioning of theelectrodes.

In another embodiment, the catheter can include suction pods and twocontrol arms. FIGS. 49A-49D show a schematic representation of thesuction catheter having two proximal control arms 21, 22. The controlarms 21, 22 can be positioned next to each other as shown in FIG. 49A.Motion of the control arms 21, 22 can allow for the catheter to beanchored and positioned as the user desires in a deliberate andrepeatable manner. The user can position the catheter in proximity tothe region of treatment and turn the suction on through one of thesuction holes. FIG. 49A shows both suction holes turned off 24 (shown asa white circles). The suction hole can be turned on 23 (shown as adarkened circle) to anchor to the tissue. The other suction hole canremain turned off 24, for example to allow its associated control arm 22to be advanced distally (see FIG. 49B). Once positioned, the suctionhole is turned on 23 while the other suction hole is turned off 24 andthe associated control arm 21 moved in similar fashion (see FIGS. 49Cand 49D). The control arms 21, 22 can also be moved in a proximaldirection using a similar on-off alternating suction mechanism.

The two control arms 21, 22 can also be concentric or in apposition toeach other (e.g., as opposed to linearly displaced) with the inner tipextended distal to the outer. In the concentric embodiment, the innertip can move distally while the outer tip is anchored. Then the distaltip suction can be turned on and the outer tip is moved until justproximal to the distal tip. The catheter can rotate around the suctionpods (i.e. control arms with suction holes) to achieve lateral motionand/or energy transmission. The suction pods can be made out ofconductive material or coated with such to act as the electrodes 6. RFcurrent can be passed between each of the suction pods/electrodes toperform the ablation, sensing, stimulating and/or mapping. There can betwo or more suction pods/electrodes per catheter.

As shown in FIG. 50, the catheter 63 can include suction holes 5 or podswithout the use of multi-tipped configuration described above. Thecatheter 63 can incorporate multiple suction holes 5 and electrodes 6can be placed adjacent to or near the suction holes 5 to anchor theelectrodes 6 to the tissue 83. Movement of the catheter 63 and suctionholes 5 along the tissue 83 can occur without the use of cables ortension wires for movement. A long continuous energy transmission linealong the tissue 83 can be created.

FIGS. 51A-51C show a closer view of the suction catheter 63 creating along continuous energy transmission line along the tissue 83 and themanipulation of the distal tip of the suction catheter 63. The catheter63 can be moved over the tissue 83 without losing initial position. Thecatheter 63 manipulation sequence can vary. In an embodiment, bothsuction holes 5 a, 5 b can be turned on such that the catheter 63 isanchored onto the tissue 83 (FIG. 51A). The suction in the distal hole 5a can be turned off and a pull wire 20 withdrawn proximally to bend thecatheter 63 and cause a backward motion (FIG. 51B). Suction can then beturned on in the distal hole 5 a and turned off in the proximal hole 5 bto allow the catheter 63 to straighten out (FIG. 51C). The suction canthen be turned on in the proximal hole 5 b and energy transmissioninitiated. This process can be repeated to create an energy transmissionline in a first direction (e.g. proximally). Suction can also beactivated in the opposite manner such that the catheter is moved forward(e.g. distally). The catheter 63 can include a laser cut pattern 3, forexample between each suction hole 5 a, 5 b that increases flexibilityand allows for lateral movement of the catheter 63.

In an alternate design, suction can be turned on to maintain theposition but not for anchoring the catheter 63 for movement. In thisembodiment, the push element 97 can be used as an alternative to suctionforces to oppose the pull force provided by the pull wire 20 to bringthe distal tip closer to the proximal tip as shown in FIG. 51B. The pushelement 97 can also be used to straighten the catheter 63 or to orientit using the flexible laser cut pattern 3.

FIGS. 52A-52D illustrate another example of an electrode systemincluding a concentric inner suction catheter 4 and an outer electrodecatheter 71. The inner catheter incorporating suction lumen 4 can bemovable and steerable and can extend beyond the distal tip of theelectrode catheter 71. Once the suction tip is firmly anchored onto thetissue 83, the electrode catheter 71 can be manipulated to be in contactagainst the tissue 83. Electrodes 6 can be mounted on the electrodecatheter 71 and can also be mounted at the tip of the suction catheter4. After an energy transmission line is created the electrode catheter71 can pivot or swivel around the suction catheter tip 4 and transmitenergy to the opposite side without losing its initial position. Anirrigation mechanism can be included and used in conjunction with theelectrode system to keep the tissue cool during the procedure asdescribed above.

FIGS. 53A-53E illustrate another embodiment of a suction catheter thatincludes an expandable portion. The electrode catheter 27 can include asingle aspiration lumen and a movable inner shaft 29. The electrodecatheter 27 has an internal lumen with multiple openings which themovable inner shaft 29 can translate over and cover. In this manner, theinner shaft 29 can selectively control the amount of suction by coveringthe specific sections of the catheter 27. In this embodiment, noseparate suction lumen need be connected to each of the aspiration endsall the way back to the handle. The catheter 27 can be contained withinan outer sheath 31 for ease in delivery (see FIG. 53D). The main body ofthe electrode catheter 27 (between the outer sheath 31 and theretractable shaft 29) can be made of a flexible or super-elasticmaterial such as Nitinol or other material. Also, shown in thisembodiment is a mechanism that allows for the passage of a cooling fluidonto the surface of the catheter through holes 7 to cool the electrodes6 and the surrounding tissue 83. Saline 30 can be used for irrigationthrough the holes 7 also as described in more detail above.

FIGS. 54A-54D show another embodiment of a suction electrode catheterthat includes an expandable portion. In this embodiment, the catheterelectrode system includes inflatable elements 34 having electrodes 6disposed thereon, such as on the surface of the inflatable elements 34.The inflatable elements 34 can be an inflatable balloon with acorresponding inflation lumen(s) 36. A suction lumen 4 and correspondingsuction holes 5 can form multiple suction pods 67 disposed along thelength of the catheter at various intervals that stabilize the catheterand assure good contact with the target tissue to be ablated, forexample a moving target tissue such as the myocardium. The catheterbetween each suction pod 67 can include a laser cut pattern 3 forincreased flexibility in positioning of the electrodes, as describedherein. FIGS. 54B-54D show the various stages of the catheter frompre-inflation to fully inflated and engaged with the tissue.

FIGS. 55A-55C show another embodiment of a suction electrode catheterthat includes an expandable portion. The catheter electrode system caninclude expandable elements 43 having electrodes 6 disposed thereon. Thelinear electrode catheter 71 can use a combination of expandableelements 43 and aspiration to anchor the device and transmit energy tothe target tissue. The expandable elements 43 can be flexible membranesor balloons having electrodes 6 of electro-conductive ink depositedthereon as described above. The expandable elements 43 can be shaped tocreate an opening to the tissue when inflated and allow for aspirationand anchoring. An aspiration lumen 4 can connect each of the expandableelements 43 and can be controlled at the handle (not shown). Aretractable shaft can be used to control suction of the individualsuction pods. In another embodiment, each suction pod can beindividually controlled via separate aspiration lumens. The aspirationholes 5 create a gap between the aspiration lumen 4 and the tissue. Thisseparation allows for the tissue to be drawn into the opening of theexpandable element 43 and be in full contact with the electrodes 6without blocking flow to the aspiration lumen 4 itself. The distal endof electrode catheter 71 can be flexible between each suction pod or mayinclude a laser cut pattern 3 and can be manipulated for best appositionto the tissue. Irrigation holes (not shown) can also be included at eachsuction pod to allow for saline to flow through and prevent clotting ofblood in the suction pods. An electrode assembly 105 that includes oneor more suctions elements can be used to treat the internal space of anorgan target tissue via electrodes positioned inside or outside theorgan. For example, for treatment of atrial fibrillation within the leftatrium, the electrode assembly can produce endocardial or epicardialablation lesion lines.

FIGS. 56A-56E illustrate various embodiments of a rapid exchangeelectrode sheath 77 that can be positioned over an anchoring catheter 11that is fixed to the tissue via suction holes 5 a, 5 b, 5 c as describedin embodiments above. In this embodiment, the electrode catheter 77 canhave one or more rings 64 near the distal end through which theanchoring catheter 11 can extend. These rings 64 as well as the proximalportion of the electrode catheter 77 can be oriented such that they donot obstruct the suction holes 5 a, 5 b, 5 c as shown in FIG. 56A. Itshould be appreciated that although only three suction holes aredepicted in the figure, more or fewer suction holes are consideredherein. FIG. 56B shows the electrodes 6 coupled to an anterior portionof one or more of the rings 64 of the catheter 77 to minimizeinterference with the suction holes 5 a, 5 b, and 5 c. An expandableelement 66 can be included that has an inside reflecting surface 79 toallow for vision through a fiberscope 78 with an angle of view 82towards the tissue. The reflecting surface 79 can have holes (not shown)that allow for a mechanism such as a water jet to contact the tissue andprovide a clear field of view for the fiberscope 78. Although areflecting surface 79 and water jet are depicted, it should beappreciated that vision can be accomplished with the use of only thefiberscope 78. FIG. 56C shows an electrode catheter 77 having a distalcurved tip 86 that can press in a downward direction on the anchoringcatheter 11. This mechanism helps to keep the suction hole(s) 5 a, 5 b,5 c against the tissue and to provide for a better anchoring.

FIG. 56D shows a guiding wire 85 extending through the anchoringcatheter 11 that can be used to orient the anchoring catheter 11 to anoptimal or better place for the suction holes 5 a, 5 b, and 5 c to pressagainst the tissue. As mentioned in previous embodiments, the anchoringcatheter 11 can be flexible with little torque resistance to enhance itsability to orient the suction holes 5 a, 5 b, and 5 c against thesurface of the tissue at a variety of angles. The anchoring catheter 11can also include a retractable hollow shaft 84 to provide more rigidityand torque control for placing the suction holes 5 a, 5 b, 5 c againstthe tissue. In an example, a user can orient the wire 85 to obtaincontact and anchoring of the most distal suction hole 5 c against thetissue. The user can pull back and rotate the shaft 84 in combinationwith manipulating the wire 85 to orient the second most distal suctionhole 5 b to contact and engage with the tissue. The next most proximalhole 5 a can be similarly oriented and the shaft retracted to allow forall the suction holes 5 a, 5 b, 5 c to be actively anchored against thetissue. Once the anchoring catheter 11 is properly oriented and stable,the electrode catheter 77 can be advanced and retracted over the suctionholes 5 without loosing adhesion against the tissue. This provides for aquicker and more efficient energy transmission, for example for thepurpose of ablation and mapping. FIG. 56E shows the electrode catheter77 movement relative to the anchoring catheter 11 against the tissue 83.

Methods of Manufacture and Materials

Various techniques can be employed in the manufacture of the devicesdescribed herein. In an embodiment, the flex circuit 89 can beconstructed to optimize for an overall low profile of the electrodeassembly 105. The flex circuit 89 can have temperature sensors 90 thatcan be powered through one of the conductive traces 16 of the flexcircuit 89. This eliminates the need for an additional assembly junctionon the membrane 64. The temperature sensors 90 can share a conductivetrace 16 with a mapping electrode 51. Sharing the conductive traces 16allows for narrower flex circuits 89 and an overall lower profile of theelectrode assembly 105. A single flex circuit 89 can split into at leasttwo branches 87 to reduce the number of parts and ease of assembly.There can be only one flex circuit 89 that splits into all the branches87 of the flex circuit 89 needed to power the electrodes 6. The distalend of the flex circuit branches 87 can contain sacrificial tabs 102that allow for proper positioning of the branches of the flex circuit 89during assembly.

The flex circuit main leads 17 of the flex circuits 89 can be routedfrom the proximal end (near a handle or actuator) of a catheter shaft 57through the catheter lumen to the distal end. The flex circuit mainleads 17 can divide into two or more branches 87 and can be folded overthe membrane 34 from either a proximal region or a distal region of themembrane 34. The membrane 34 can be mounted on a temporary mandrelsupport with inflation ports to maintain a constant expanded stateduring assembly. The flex circuit sacrificial tabs 102 can be mated toan assembly fixture for consistent tensioning of all branches of theflex circuit. The fixture can be designed to hold the membrane 34 andthe flex circuit 89 in a pre-determined position relative to the other.For a streamlined bond of the flex circuit 89 to the membrane 34, theflex circuit branches 87 can be pressed firmly against the membrane 34surface while an agent, such as adhesive, is applied and cured. This canminimize the profile due to, for example, an excessive amount of agentapplied. Adhesive can be applied to the underneath surface or bottomsubstrate layer of the flex circuit 89, which will be in contact withthe membrane 34. This can be accomplished through the use of a roboticsystem, which can apply precise amounts of adhesive at appropriatelocations on the flex circuit 89.

As shown in FIG. 59, the assembly fixture can include a centering andinflation pin 106 and the fixture base 107. The flex circuit 89 can beinserted through a central slot 108 in the fixture base 107 and thebranches 87 directed to their respective radial pattern slots 109. Themembrane 34, a toroid-shaped balloon in this example, can be mounted onthe centering and inflation pin 106 and the pin is inserted through thecenter slot 108 of the fixture base 107 and secured in place. Aregulated, low pressure air supply can be used to inflate the membrane34 to the desired level once on the fixture 107. The sacrificial tabs102 of the flex circuit 89 can be mated to the radially-spaced slots 109of the perimeter of the fixture base 107, maintaining a consistentposition of the flex circuit 89 relative to the expandable membrane 34.Once the flex circuit 89 and the membrane 34 are properly located andsecured, the agent can be applied and cured.

In FIGS. 61A-61C, 62A and 62B are illustrated various means by whichcatheter shafts may be interfaced to the expandable membranes 34associated with the electrode assembly 105. FIG. 61A and detailed viewsFIGS. 61B and 61C illustrate how the outer diameter (OD) of an innershaft 134 and an outer shaft 57 may be interfaced to the varioussurfaces of an expandable member 34. In FIG. 61B is illustrated anexpanded view of an interface in which the outer surface 135 of theexpandable membrane 34 is interfaced to the OD of the inner shaft 134and the inner surface of the expandable membrane 34 is interfaced withthe OD of outer shaft 57. In FIG. 61C the interface to the outer shaftremains the same as that illustrated in FIG. 61B, however the innersurface of expandable membrane 34 is interfaced with the OD of innershaft 134. Although not shown, a single shaft may also be used tointerface with the distal and proximal interfaces of the expandablemembrane 34. In this embodiment, a spacer can be used at the distal end.Alternatively, both interfaces on the expandable structure can befabricated at the same inner diameter (ID).

FIGS. 62A and 62B illustrate the interface of FIG. 61B where theexpandable member portion of the interface incorporates a thickenedsection 35. FIGS. 63A and 63B illustrate the interface of FIG. 61C wherethe where the expandable member portion of the interface incorporates athickened section 35 and additional structure associated with theelectrode assembly 105 are also incorporated. The interface of FIGS.63A-63C has particular advantage when presenting electrodes on thedistal surface of the electrode assembly 105 as all portions of theshaft to which the expandable member 34 is interfaced reside proximal tothe distal end of the shafts on inflation or a portion of the expandablemember 34 is substantially distal to the distal end of the assembly orthe distal end of the shaft.

The electrodes 6 can be sprayed onto the flex circuit 89 and membrane 34while still mounted on the temporary support mandrel. The electrodes 6can cover each conductive pad 59 for electrical connection to the flexcircuit trace 16 and a relatively large portion of the surroundingmembrane 34 surface and over the insulated portions of the flex circuit89 itself. The electrodes 6 can be formed by using a mask over themembrane 34 during the deposition process, which can spray over themembrane and the mask alike. Once the ink is cured, the mask can beremoved. An alternate technique is to use automated robotic systemswhich may be programmed to precisely and accurately spray only thedesired electrode surfaces without the presence of a mask.

The electrodes 6 can be formed before or after the flex circuit isbonded to the base membrane structure. FIG. 2A shows an electrode 6deposited onto the membrane 34 first. The trace 16 of the flex circuit89 can be laid over the membrane 34 with the conductive pad 59positioned directly over the electrode 6. An electrically conductiveadhesive layer 95 can be laid over portions of the electrode 6 to adhereto the exposed conductive layer 96. Non-conductive adhesive 95 can beused to bond to the rest of the membrane 34 and trace 16. FIG. 2B showsthat the trace 16 can be first bonded to the membrane 34 using anadhesive which does not need to be conductive. The conductive pad 59 canface outward from the membrane 34 surface such that it is not in directcontact with the membrane 34. The electrode 6 can then be laid over theconductive pad 59, the adjacent insulated flex circuit 89 portion, andthe membrane 34.

FIG. 2C shows the trace 16 of the flex circuit 89 traveling from insidethe membrane 34 through the membrane surface. The electrode 6 canalternatively be placed first, in which case the exposed conductive pad59 of the trace 16 can face inwards to be in contact with the electrode6. FIG. 2D shows the flex circuit 89 manufactured at the same time asthe membrane 34. As shown, a layer of membrane 34 material can be theinner-most layer, followed by placement of the flex circuit 89 andtraces 16 with the exposed conductive pad 59 facing out. The conductivepad 59 of the trace 16 can be masked to deposit the remaining layers ofmembrane material to encapsulate the flex circuit 89. Lastly, theelectrode 6 can be laid over the exposed conductive pad 59 of the trace16 and the membrane 34. The electrode 6 in this embodiment can also be apolymer impregnated with conductive material. FIG. 2E shows anembodiment where the electrode 6 is manufactured at the same time as themembrane 34. The electrode 6 can be embedded with the membrane 34 layerand the electrode material may be impregnated with the membrane materialto enhance adherence. The trace 16 can then be placed over the electrode6 with the exposed conductive pad 59 in contact with the electrode 6.

Methods of Use

As described previously, the devices and method described herein are notlimited to use for atrial fibrillation. It should be appreciated thatthe following is for example only and that other indications areconsidered herein.

The devices described herein can be used for the ablation of themyocardium, for example for the treatment of atrial fibrillation. Thepulmonary veins, which are known to cause irregular signals, can beelectrically isolated from the rest of the atrium. Aberrant tissue onother areas of the atrium that can cause irregular electrical signalscan be found and ablated. The electrode assemblies described herein canconform to the different anatomical sites within the atrium toelectrically eliminate these abnormal signals. In an embodiment, theelectrode assembly for use in treating atrial fibrillation includes aballoon shaped membrane in the shape of a sphere or a toroid allowingfor large diameter to be positioned against the antrum of the pulmonaryvein for circumferential lesions. Another site where such electrodeassemblies have application is in the treatment of mitral prolapse. Inthis treatment the electrode structure may delivered to the mitralvalve, inflated, such that the electrode structures interface with theannulus of the mitral valve. When lesions are induced in the annulus ofthe mitral valve, the collagenous tissues comprising the annulus willshrink. Such treatments are effected by other means with the outcome ofdecreasing mitral valve regurgitation. Such a treatment can be useful inany of the valves of the heart. Alternatively, an electrode assemblyincorporating a cylindrical balloon shaped membrane element may be usedto treat atrial fibrillation within the pulmonary vein, where a helicallesion pattern can be used to advantage as a means of limiting stenosisresultant from the ablative injury. Yet another site where such aconfiguration has particular advantage is in the treatment of hypertension by ablating sympathetic nerves peripheral to the renal arteries.The ability to create a helical lesion within the renal artery withoutrequiring repositioning of the electrode structure, either by activationof a set of helically arrayed electrodes or addressing a subset of arectilinear array to create a helical lesion as described herein hasadvantage over the art presently in use. With reference to the luminaltreatments just described, patterns other the helical lesion can providethe same outcome. Such patterns are those in which the projection oflesions on a plane normal to the long axis of the treatment lumen createa complete circle of overlapping regions.

In an embodiment, the electrode assembly 105 can be sheathed using asheathing fixture 103 and introduced into a sheath that is placed at theappropriate entry point, the femoral vein for example (see FIGS.57A-57C). The sheathing fixture 103 can be a block with a predefinedinternal diameter for the electrode assembly 105. The fixture 103 can bemanufactured as two halves that are slidable and interlockable to eachother as shown in FIG. 57A. A sheathing tube 104 can be used inconjunction with the sheathing fixture 103 in that the tube 104 canslide into the sheathing fixture 103 until it reaches a hard stop asshown in FIGS. 57B and 57C. The inner diameter of the tube 104 can matchthat of the fixture 103. To sheath the ablation assembly 105, thecatheter can be placed within the sheathing fixture 103 such that theassembly 105 is outside of the fixture 103 at one end as shown in FIG.58A. The shaft 57 can also be placed with the two halves of thesheathing fixture 103 still separated. The assembly 105 can be pulledinto the inner portion of the sheathing fixture 103. The tube 104 can beinserted into the fixture 103 until it reaches a hard stop. The shaft 57and the electrode assembly 105 can be pushed into the tube 104 andseated within the tube 104. Once the assembly 105 and shaft 57 aresecurely sheathed into the tube 104, the fixture 103 can be removed fromthe assembly 105 by separating the two halves of the sheathing fixture103. The sheathing tube 104 can be to introduce the assembly 105 into asheath that is placed to reach the desired target tissue. The assembly105 is then pushed out of the sheathing tube 104 and travels within theintroducer to reach the target site. The sheathing tube 104 remainsproximal to the assembly and does not travel within the introducersheath 117.

An alternate means of sheathing prior to introduction to the introduceris illustrated in FIGS. 58F-58H. The three primary stages of thisprocess are represented in FIGS. 58F-58H and are described as follows.In this embodiment an alternate sheathing tube 128 is mounted on theouter shaft 57 at the time of manufacture as shown in FIG. 58F. Thesheathing tube 128 and assembly 105 are moved relative to one anothersuch that assembly 105 is collapsed by alternate sheathing tube 128 asindicated in FIG. 58G. As the relative motions are continued electrodeassembly 105 is captured and contained within the alternate sheathingtube as shown in FIG. 58H. The alternate sheathing tube 128 andelectrode assembly 105 are then introduced through an introducer valve126 into the introducer sheath 127. Sheathing tube 128 may be a shortsection which interfaces with the proximal section of outer shaft 57, ormay be close to the entire length of the outer shaft 57 such that it canbe operated from the handle and can be used while the electrode assembly105 is resident in within the luminal system under treatment.

In yet another embodiment a sheathing tube may or may not be required.This embodiment is represented in FIGS. 581-58K. In this embodiment theinner shaft 58 and the outer shaft 57 are moved relative to one anothersuch that the electrode assembly 105 is shifted from its expandedconfiguration to a delivery configuration as indicated in the transitionpictured from 58I-58J. As illustrated in FIG. 58K, electrode assembly105 is shifted into introducer sheath 128 through and introducer valve126 and the device is ready for transport to the treatment site.Alternately, the device in the configuration of FIG. 58J may bedelivered with a sheathing tube such as those described herein.

The alternate delivery sheath 128 is illustrated in FIG. 65. Thealternate sheathing tube can have multiple tubing layers and isconfigured to be captured on the outer shaft and present a soft andcompliant member at the interface to the electrode assembly 105. It istypically mounted on the outer shaft at the time of manufacture. Thedevice is described as follows. A soft jacket 129 fabricated from acompliant material such as PEBAX encapsulates at least the distal end ofa stiff jacket 130. The soft jacket 129 also extends beyond the distalend of the stiff jacket 130 such that as the alternate delivery sheath128 interfaces with the electrode assembly 105 a compliant member ispresented assuring no damage to the electrode assembly occurs as it isbeing compressed into its sheathed configuration. The stiff jacket 130can be manufactured of stiff materials such as polyimide. This proximalend of this assembly is surrounded by base tube 122 which can bemanufactured of materials having strength such as polyimide. At theproximal end mounted within the base tube 132 is the stop tube 131 whichis configured to collide with a feature on the outer shaft 57 (notshown). The stop tube 131 can be manufactured of materials such aspolyimide. Given the characteristics of the materials presented otherscan be appropriately chosen as replacements by those with knowledge inthe art.

The assembly 105 can be delivered to the left atrium and the membraneexpanded and placed at the antrum of one of the pulmonary veins. Theoverall shape of the membrane can be visualized using the electrodesthemselves as the conductive metallic material of the electrodes canprovide visualization under fluoroscopy. The radiopaque markers can beused to determine exact location of each electrode based on the markerorientation. The mapping electrodes can be used to measure initialelectrical signals and can later confirm electrical conduction blockpost ablation. The user can select which electrodes to turn on, whichones to leave off, and which ones to set to a higher or lower powersetting based on their contact with the tissue. The various methods ofcontact detection as described above or a fiber optic can be used toconfirm contact of the electrodes with the tissue. The device is thenset to the appropriate power and temperature settings, irrigation turnedon to the desired level, and energy transmission initiated. The mappingelectrodes can be used now to determine successful conduction block.Once conduction block is achieved, the catheter and moved over to thenext target location, another pulmonary vein or atrial wall, forablation.

FIG. 64 illustrates a complete system 1000 for using the electrodeassembly 105. The system incorporates a visualization system 1004, asource of ablative power 1002, an irrigation fluid source 1003interfaced to a pump possibly incorporating an irrigation fluid coolingmeans 1005, an interface cable 1001, a catheter handle 1006incorporating additional controls, a catheter incorporating a shaft 57connected to the distal end of the electrode assembly 105 and associatedinner assemblies, the electrode structure 105, and a guide wire 1007.

It should be appreciated that variations of the disclosed devices,assemblies, and methods can exist. It should also be appreciated that avariety of elements described herein can be used individually or in avariety of combinations. Features described herein in the context withor respect to one exemplary device or assembly can be implementedseparately or in any suitable sub-combination with other exemplarydevices or systems.

It is to be understood that this subject matter described herein is notlimited to particular embodiments described, as such may of course vary.It is also to be understood that the terminology used herein is for thepurpose of describing particular embodiments only, and is not intendedto be limiting. Unless defined otherwise, all technical terms usedherein have the same meaning as commonly understood by one skilled inthe art to which this subject matter belongs.

While this specification contains many specifics, these should not beconstrued as limitations on the scope of what is claimed or of what maybe claimed, but rather as descriptions of features specific toparticular embodiments. Certain features that are described in thisspecification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable sub-combination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a sub-combination or a variation of a sub-combination.Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Only a few examples and implementations are disclosed.Variations, modifications and enhancements to the described examples andimplementations and other implementations may be made based on what isdisclosed.

1. A minimally invasive visualization assembly configured to visualize atarget location in a patient's body, comprising: an elongate deliverydevice comprising a guidewire lumen; a plurality of cameras mounted tothe elongate delivery device; and a closed inflatable membrane securedto the elongate device, the elongate device being in fluid communicationwith the closed inflatable membrane and allowing a fluid to be deliveredinto the closed inflatable membrane through the elongate device toinflate the closed inflatable membrane, wherein the plurality of camerasare disposed within the closed inflatable membrane and configured tovisualize substantially 360 degrees around a longitudinal axis definedby the elongate delivery device to which the plurality of cameras aremounted.
 2. The assembly of claim 1 further comprising a camerasubassembly comprising the plurality of cameras, wherein the camerasubassembly is mounted to the elongate delivery device.
 3. The assemblyof claim 2 wherein the subassembly comprises at least one light source.4. The assembly of claim 1 further comprising a plurality of camerasubassemblies mounted to the elongate delivery device, the plurality ofsubassemblies comprising the plurality of cameras.
 5. The assembly ofclaim 4 wherein the plurality of subassembly comprise at least one lightsource.
 6. The assembly of claim 1 wherein each of the plurality ofcameras has a field of view of substantially 120 degrees around thelongitudinal axis defined by the elongate delivery device to which theplurality of cameras are mounted.
 7. The assembly of claim 1 wherein theplurality of cameras each have a field of view that is fixed.
 8. Theassembly of claim 7 wherein each of the plurality of cameras is directedabout 15 degrees relative to the longitudinal axis defined by theelongate delivery device to which the plurality of cameras are mounted.9. The assembly of claim 1 wherein each of the plurality of cameras hasa field of view that is adjustable.
 10. The assembly of claim 1comprising three cameras, the three cameras being distributed about 120degrees apart around the longitudinal axis defined by the elongatedelivery device.
 11. The assembly of claim 1 wherein fields of view oftwo of the plurality of cameras overlap in an overlap region.
 12. Theassembly of claim 11 wherein a field of view of each of the camerasoverlaps with a field of view of an adjacent camera.
 13. The assembly ofclaim 12 wherein the overlap region is used to knit the overlappingimages together into a contiguous image.
 14. The assembly of claim 1wherein the closed inflatable membrane has a plurality of holes thereinconfigured to allow the fluid to pass through the holes.
 15. Theassembly of claim 1 wherein the elongate device comprises a flexibleshaft.
 16. The assembly of claim 1 configured for percutaneous delivery.17. The assembly of claim 16 configured for endoluminal delivery. 18.The assembly of claim 16 configured for vascular delivery.
 19. Theassembly of claim 1 further comprising a light source.
 20. The assemblyof claim 19 further comprising a plurality of light sources.
 21. Theassembly of claim 20 further comprising a subassembly comprising theplurality of light sources.
 22. The assembly of claim 21 furthercomprising a plurality of subassemblies, the plurality of subassembliescomprising the plurality of light sources.
 23. The assembly of claim 20wherein each of the plurality of cameras is disposed adjacent to atleast one of the plurality of light sources.
 24. A minimally invasivevisualization assembly configured to visualize a target location in apatient's body, comprising: an elongate delivery device comprising aguidewire lumen; a plurality of cameras secured to the elongate deliverydevice proximal to a distal end of the guidewire lumen; and a closedinflatable membrane secured to the elongate device, the elongate devicebeing in fluid communication with the closed inflatable membrane andallowing a fluid to be delivered into the closed inflatable membranethrough the elongate device to inflate the closed inflatable membrane,wherein the plurality of cameras are disposed within the closedinflatable membrane and configured to visualize substantially 360degrees around a longitudinal axis defined by the elongate deliverydevice to which the plurality of cameras are secured. 25.-46. (canceled)